Questions About Building a CC Skimmer [Archive] - Reef Central Online Community Archives

LiquidShaneo

12/18/2000, 11:18 AM

I am contemplating building my own 4' airstone driven counter current skimmer and am wondering if anyone has done this and if so what their results were. I am using the following book to guide me in the proper design of the skimmer for my tank:

Aquatic Systems Engineering: Devices and How They Fuction by P.R. Escobal

And I am using Larry Jackson's PVC component listings that he used for his DIY skimmer (plans available from http://www.ozreef.org/). Has anybody else used this book to DIY a skimmer for their tank and if so, how accurate was the engineering principles behind it? I'd like to hear other peoples' experiences. I basically have all the equipment to run this skimmer. I just need to build the skimmer body.

Thanks in advance,

liquid

LiquidShaneo

12/18/2000, 02:31 PM

Aaron Shelley

12/18/2000, 11:16 PM

I have built about 10 or 11 skimmers over the last 9 years. The first ones were as you plan to build. I prefer the venturi ones as they are more productive and require less maintenance size being equal.

LiquidShaneo

12/20/2000, 03:58 PM

Anyone else?

12/20/2000, 04:31 PM

I have read that book and I chose to use 6" PVC to build my skimmer.

I will disagree with Aaron and say that I like airpump skimmers better than venturi. There, now are you thouroughly confused? :)

The only type of skimmer that I would consider replacing my skimmer with is an aspirating skimmer, i.e. Euroreef.

If you need some Luft pumps I have a wooden box with four of them inside of it. I'd let'em go real cheap :)

Endoplasmic

12/20/2000, 05:37 PM

I'm a newbie sorry... what's a luft pump... and if you meant lift pump.. .what do those do and how do they function?

Snailman

12/20/2000, 09:03 PM

I am a CC skimmer fan also. :) They are the only design where you can adjust the air water ratio and that are also more plankton friendly that the other designs. Ron of Ron's Saltwater Heaven makes CC skimmers and he puts a regular PVC pipe cap on the bottom. His reasoning is so that stuff does not collect down at the bottom and he is right it doesn't. :) I think that Ian McDonald has a better design and I can email you a copy of it if you want it. The air you can pump into a CC skimmer with out it flooding is limited by the reaction tube diameter. Ron uses a 2" tube and Ian uses a 3 1/2" tube. I have built one of Ian's top ends for my Ron's skimmer and I am going to put it on this weekend. It should make the skimnmer really kick rear end. :D

Flatlander

12/20/2000, 09:49 PM

Right on about the neck size, Snailman.
I finally gave up on the one I was trying. Gave it to my lfs to use on his downstairs sumps. What a waste of $200
Were building a larger model, such as you guys are trying. For sure the returns will be two- one inch pipes, so it can handle some flow.
We are also making a larger collection throat, an adjustable size neck piece and a large collection cup. It will take a feed from an Iwaki 20 pressure pump and use a pair of 6in. airstones.
Since our posts on this before, we have found that the smaller airstones do not make a fine enough bubble from big airpumps. There was no way not to overdrive the skimmer. The new one will correct all of this, we hope.
Also tried a 5ft. venturi with a large return system. Tried to drive 2 airstones in it and again the same problem of overdriving the skimmer with a large & very turbulent action in the neck. Again to rough for a good skimmate.

Snailman

12/21/2000, 06:29 AM

Doug... two 1/2" pipes should be plenty big enough to carry the return water in a CC skimmer. The aim is more air not more water so the air/water ratio goes up to improve the efficency.

Flatlander

12/21/2000, 10:42 AM

But,but, :D, the problem I have now is that as good as my Euroreef is, I do not pass enough of the tanks water.
The reason for the bigger returns was to allow the use of a bigger pump and still allow the room to crank up the stones which I could not do in the smaller skimmer. No!

Snailman

12/21/2000, 10:40 PM

Originally posted by Endoplasmic
I'm a newbie sorry... what's a luft pump... and if you meant lift pump.. .what do those do and how do they function?

We mean Luft. :) It is a model of Tetra air pump. You will see it refered to as the Tetra Luft or just The Luft. :) It is a high pressure pump that can drive large air stones under 7' of water so they are popular with CC skimmer owners.

Snailman

12/21/2000, 10:48 PM

Doug... The one tank per hour for a skimmer is pure bunk. What you want a skimmer to do is remove the gunk from your water. The higher the air/water ratio is the better the skimmer works up to a ratio of 16/1 where it's efficency levels off. You can only pump so much air into a wooden airstone and still keep a small bubble size so if you increast the water flow you are making the skimmer less efficent not more. If you can get a hold of the 1999 annual USA Marine Fish and Reef there is a wonderful article that explains this much better than I have. :) I run my Ron's skimmers at a very low water rate and drive the air stones with a Medo ACO902 air pump. :D

LiquidShaneo

12/21/2000, 11:16 PM

I agree with Snailman on this: "The one tank per hour for a skimmer is pure bunk." This is a pretty common misconception from what I've seen... Doug, the faster you run water thru your skimmer the *less efficient* your skimmer becomes. You need to maximize the amount of air that hits each water "glob" to maximize waste export...*not* the other way around. An air bubble can only hold so much waste so you want to pass as much air past dirty water as possible to remove as much of the krud as possible per unit volume. Pump up the air and turn down the water flow...

liquid

12/22/2000, 02:20 PM

Shane I was thinking about making my own skimmer also but decided to stick with what I got since I'm not getting a bigger tank yet. But use extruded tubing for the skimmer body. Not the pvc that you can't see into. With the extruded just use a 6" cap on both ends and glue it with weld-on #16, this stuff is cheap enough to use for a pro look.

Snailman

12/22/2000, 04:28 PM

I am a fan of PVC skimmers so they stay clean inside but if you decide to build one out of acrylic I wiil be glad to give you some help on the flanges. Also http://www.usplastic.com is a good place to get acrylic sheet and tube as welll as all kinds of cool stuff for your DIY projects and they are super to deal with. :)

pacmans

12/22/2000, 06:02 PM

Hello everyone interesting thread

Doug I have to agree also with snailman on this que. of the ratio of (water flow vs air)
In water tretment plants through out the US and Canada and other parts of the world they use foam frictionation or skimming in the purifying of water pollution in tretment plants and have for some time.
The motors that drives the air blowers are big say 150 to 200 hp, the blower is about 5' across and about 6' high and I can say vary noisy the air then is blown into a water contact channel and comes in contact with the slow moving water to allow more air contact time with the effluent there are also millions of good guy bugs in the chamber that also break down the effluent but that is a microbiology
thread and a little off topic here.

(just a wierd kind of fact for any one reading this)

If you were to fall accidently into the channel you would sink like a rock because the buoyancy of the water has been take out by the ammount of air being pumped in and the slow movement of water.
I guess the rate of water passing through the skimmer would depend on what you set the pump output at via a valve.

Just wondering though with cc skimmers don't you find you have to tweek them alot to get the air just right?
and is the ratio 16/1 is that 16 cubic/ft of air to one gallon of water?

pacmans

Flatlander

12/22/2000, 08:37 PM

So are we saying that a skimmer with an injection system or downdraft and runs on a large pump, with large volumes of water is not as efficient? I thought it was the large amount of water passed through them that makes them so efficient at skimming large tanks?
My cc did work better with less water flow and more air but IMO, was not processing much water at that rate.
Does not a larger chambered Euroreef with 2 or 3 pumps, put more water through it, thus allowing it to skim larger tanks than my single pump model?

pacmans

12/22/2000, 09:30 PM

Hi doug
I am not sure about how much water should go through the skimmer.
I was always under the same impression as you were until rescently a hi ratio of water to air is what all the lfs tell us reef hobby nuts.
The more water through the skimmer meant more skimming the tank of waste.

Newbee QUES here

But I have always wondered if there was a good rule of thumb for this ratio that is why I found this thread interesting to see if some one out there new what is an ideal turn over rate for a tank of any given size?

But I am also curious do you have to adjust the CC skimmers more often to dial them in but once they are set do you have to play with them alot or is it locked in until your air stone needs replacing and how often would that be

I am interested in a CC skimmer for a future tank just like to do the research first you know ask ask ask, to get a better understanding of this relationship and what is the advantage to CC this may also help liquid shaneo on the correct size to build.
Not trying to start a flame here of venturi over CC everyone has there preference just like to know more about CC

anyone

Thanks
pacmans

Snailman

12/22/2000, 09:50 PM

Doug... The problem with a venturi or pin wheel skimmer is they take a lot of water to begin with to even work. To increase the air flow you have to increase the water flow so the ratio does not change. This is why industrial scale foam fractioners are air based just like pacmans said. It is far better to pass 1/4 tank volume through your skimmer an hour and have it be real clean when it came out rather than moving dirtier water out faster. If you can find a copy of 1975 Sep Sci 10(6):673-688 there is an article that explains how this ratio was determined. It was written by S. I. Amad. Also there is a Weeks and Timmons 1992 article on the feasibility of using foam fractionation for the removal of disolved and suspended solids from fish culture water in Aquaculture Eng 11:251-265.

pacmans...The ratio is cubic feet of air to cubic feet of water or any other measure as long as both the air and the water are in the same measurement. One cubic foot of water is 7.5 gallons.

[Edited by Snailman on 12-22-2000 at 09:04 PM]

LiquidShaneo

12/23/2000, 12:19 AM

I again totally agree w/ Snailman. Grab yourself a copy of the two articles that Snailman mentioned and also grab yourself a copy of Aquatic Systems Engineering: Devices and How They Fuction by P.R. Escobal (which you probably can get thru interlibrary loan). They will explain *everything* about efficiency, etc. along w/ equations and all if you really like to get into that kind of stuff (which I do!).

In case you're interested in reading about a comparison of the EuroReef skimmers with other high powered skimmers, please refer to:

http://www.animalnetwork.com/fish2/aqfm/1998/nov/product/default.asp

Later!

liquid

golfsuper

12/23/2000, 12:36 AM

Guys,

I thought I was one of the few remaining CC users. I guess I'm not alone after all. I always think of trying a venturi or other style, but my CC skimmer is just too reliable. I'm one toying with the idea of reduced skimming, so if I lose efficiency with a CC, so be it. The operative phrase you guys are all dancing around it "contact time." BTW liquid, I might happen to have a juicy 5' section of 4" acrylic in the shop that I could let go of. I know my wife would gladly pay the shipping to get it out of her way. HeHe.

golfsuper

pacmans

12/23/2000, 01:54 AM

Hi snailman and anyone who read this far down the page

How big are the air pumps on the cc out there say in the 4' to 6 ' range

Anybody with a 4'to 6' skimmer out there that knows there air pump output pressure

Anybody thanks
pacmans

Snailman

12/23/2000, 08:37 AM

Originally posted by pacmans
Hi snailman and anyone who read this far down the page

:) We started out with an air pump for this and an air pump for that and I got real tired of listening to them all buzz and keeping them all working. I bought an indistrial strength air pump. :) It is a Medo ACO902. It pumps am minimum of 1.94 CFM at a maxium pressure of 6.4psig. It is a linear piston air pump and they run for years and when they die you just replace the $35 piston. :) We drive three 5' skimmers and a bunch of other stuff with it. I think that normal people :) you a good pressure pump like the Tetra Luft.

Flatlander

12/23/2000, 11:01 AM

I use a Tetra-tec DW 96-2. Its the biggest they make/made.
Cannot crank it wide open on the 6ft. by 3in.skimmer or the 3ft. by 4in. model I tried.
Thus the reason for building the BIG one,:D.

So do you guys think the smallest Iwaki 20rlt would pass to much water through a 6ft. by 4in?
Snailman, would not the 1in. return allow for more air to be pumped in as there would be no backing up from to much water flow. I am valving them also as per yours & KW,s instructions from the previous thread.
Thanks for the reference,s guys. Going to find them. I have read some.

I just feel I must have more water passing through. I feed my 170 a ton of food. When I did this to my 70, the Euroreef handled it fine, but I feel its creeping up on me in this tank as the Euroreef may be to small for the load.

LiquidShaneo

12/23/2000, 12:07 PM

Hehe. Yeah, Snailman, I'm sure you got tired of hearing all those airpumps. I know it can get old after awhile. :) Sounds like a Tim Allen setup for that airpump! :) I've got 3 running in my den right now to power my airstone modified BakPak and my prop tank. Oh, in case you're interested in seeing my prop tank, take a look @ this: http://liquidreef.freeservers.com/prop.htm . I did some pretty unique things to acheive flow in my prop tank -- without the use of powerheads none the less! No more powerhead screens to clean and no more worries that my powerheads will short out in the tank either. The only actual electrical device I have in there anymore is a 100 watt heater. You may want to look @ this Snailman as it would be *another* use for your industrial strength airpump. :)

Personally, I'm running a Tetra Luft pump on my BakPak right now and it's rated to 7 psi. I plan to use that on my 4" diamter 4' high cc skimmer. I know that there are others that are using this same pump on higher diameter skimmers and it's working fine for them. I would definitely say the Tetra Luft will work well for you Pacmans. Here's a little bit o' trivia for you: for every 2.3 ft of water depth you go down you increase water pressure by 1 psi. So for example if you have a 4' high skimmer, the water pressure at the bottom of the skimmer is as follows:

Bottom psi = 4 ft x (1 psi/2.3 ft) = 1.73 psi

Considering that the Luft will pump against *7 psi*, you could pump air into a skimmer that's 16 ft high. That's a HIGH skimmer. lol

In case you're wondering, I purchased my Luft from Pet Warehouse on the net: http://www.petwhse.com/ for about $35 or so.

golfsuper: I'll definitely keep the 4" acrylic option open! btw...how much do you want for it? Feel free to e-mail me off-list @ chemistboy@excite.com.

Doug: I'm not sure what the flow rate of the Iwaki 20 rlt is. Sorry... :) A cc skimmer for a 170 should use a 6" diameter pipe with a flowrate of 130 gph for optimum nutrient export. Now you could also go with two 4" diameter cc skimmers or four 3" diameter skimmers inline and that would give you the same net area as one 6" cc skimmer. It's entirely up to you. :) I would definitely valve any pump running the skimmer as it will allow you to fine-tune the skimmer performance. I would use a gate valve over a ballvalve as you have a finer control over flow using a gate valve vs. a ballvalve.

I'm actually planning on using a 1" return on my skimmer just because I'm concerned with a smaller diameter return line somehow plugging up. I'd hate to come home to a flood b/c I undersized the return lines. I also plan to make an emergency overflow pipe from the skimmer collection cup back to the tank just in case a line does get plugged and the skimmer starts to back up. The water that backs up into the collection cup would then go thru the pipe and empty into the tank. Yeah, the skimmer would not function during this time, but hey, it saved my hardwood floors! :)

Plans at this point are to document how I make this skimmer and I'll post the results to my webpage. I also plan to summarize Escobal on that webpage as well using the published equations and charts. This is one thing that I have *not* seen anywhere on the net...

Thoughts?

liquid

12/23/2000, 12:37 PM

With the only exeption being the Euroreef pump, IMO, all other skimmers using venturies consume for too much electricity for the amount of air they produce. Any venturi can be put on a closed-loop; thus, allowing the air production and water throughput to be seperated. Another means to accomplish this seperation is the use of a seperate sump, for the skimmer, where the flow into the sump is controlled.

Linear piston and linear diaphram pumps are available with covers. Covered pumps will have sound ratings around 33-38 db. I am aware of Aquatic Ecosystems covered pumps and Gast covered pumps. If you know of some others please list them.

I was thinking about getting a Euroreef skimmer but, after thinking about it I decided that the money would be better spent on a powerful air pump.

To date, the only limitation I have had with my air-pump powered skimmers has been the air diffusers. I just could not get enough air to pass through the diffusers without either: (1) making the bubbles too large, (2) creating too much agitation within the skimmer.

I just made a prototype air diffuser that I have been testing for a week now. It looks very promising. This air diffuser has the bubble producing surface area of 18 6" air diffusers and has significantly less back pressure than any wooden air diffuser I have ever used. The prototype air diffuser is made from wood and uses less than 1/3 of the wood that would be used to build 18 6" stones.

The only unkown of this diffuser is it's durability. I tried to burst it with my Medo-602 and it would not split. Now, I'm just waiting to see how it holds up to two months of use. If it lasts for two months, I would like to have some other CC users try it out :)

Snailman

12/23/2000, 01:25 PM

Originally posted by KW

Linear piston and linear diaphram pumps are available with covers. Covered pumps will have sound ratings around 33-38 db. I am aware of Aquatic Ecosystems covered pumps and Gast covered pumps. If you know of some others please list them.

I got my Medo ACO902 from http://www.aquaculture-supply.com and yesterday I bought a Medo ACO602 on Ebay. :) Priming up for my 6" Reverse Carlson Surge Device. :D

Snailman

12/23/2000, 01:35 PM

Originally posted by LiquidShaneo
I'm actually planning on using a 1" return on my skimmer just because I'm concerned with a smaller diameter return line somehow plugging up. I'd hate to come home to a flood b/c I undersized the return lines. I also plan to make an emergency overflow pipe from the skimmer collection cup back to the tank just in case a line does get plugged and the skimmer starts to back up. The water that backs up into the collection cup would then go thru the pipe and empty into the tank. Yeah, the skimmer would not function during this time, but hey, it saved my hardwood floors! :)
Thoughts?

Look here -> http://www.precisionmarine.com/Accessories/Waste_Collector/waste_collector.html for a solution to the skimmer flood problem. I just built a DIY copy of three of these for our CC skimmers. :)

12/23/2000, 03:45 PM

Hey golfsuper I'll take that section of 4" acrylic if shane don't want it.

I'm wondering if you guys run your water into the skimmer in a tornado like way. I've heard a few times in this thread that if you put too much air into the skimmer they get too turbulent but I would think if the waters flowing tornado like inside the skimmer that it would be hard to make too much turbulence.

Also don't berlin skimmers have a little piece of acrylic in the very bottom of the risor tube so it'll make the water less turbulent right before it starts to make foam.

LiquidShaneo

12/23/2000, 05:19 PM

Snailman: Dude, that collection cup idea WROX! You mind sending me a pic of that DIY project as well? I've already hit you up for a ton of pix already... lol

KW: I'd be interested in hearing more about your airstone if it's all of what you say it is. You want another prototype tester? I'd be willing to do it! :D

liquid

Snailman

12/23/2000, 05:30 PM

LiquidShano... The pix will be on the way soon.

KW... I would be more than glad to do some beta testing right now. We have three CC skimmers so I could do a comparison test. Feel free to email me.

Flatlander

12/23/2000, 05:44 PM

Liquid, thanks for the figures. The Iwaki pushes 500gph. Guess thats to much by your figures.

Now that something new we have not talked about KW. Are we saying that my turbulence problems and large bubbles could be partialy caused by to small of an air pump?

Snailman

12/23/2000, 06:40 PM

Originally posted by KW
To date, the only limitation I have had with my air-pump powered skimmers has been the air diffusers. I just could not get enough air to pass through the diffusers without either: (1) making the bubbles too large, (2) creating too much agitation within the skimmer.

Chen's artice in 1994 Aquaclture Engineering found that with increased air volume in the skimmer the air superficial velocity increases there by decreasing the length of time it take for the bubble to rise so it is exposed to less gunk. The real bad part is that as the superficial velocity increases the bubble size also increases. Protein removal decreases as bubble size increases.

This is why you need a larger diameter skimmer tube to increase the air flow a lot.

LiquidShaneo

12/24/2000, 12:11 AM

I think that's part of the reason why the Euroreef skimmers work better than other venturi's: their diameter is *much* larger than I've seen listed for other skimmers on the market for a comparible sized tank.

Oh, thanks for the pix Snailman! That self sealing skimmate collector looks pretty slick! Now I've got another DIY project to work on after the skimmer is complete. My wife is gonna love this... :D

Another question Snailman: how much contact time to you estimate your 5' high skimmers have anyhow?

Thanks!

liquid

12/24/2000, 07:42 AM

Snailman,

Originally posted by Snailman

Chen's artice in 1994 Aquaclture Engineering found that with increased air volume in the skimmer the air superficial velocity increases there by decreasing the length of time it take for the bubble to rise so it is exposed to less gunk. The real bad part is that as the superficial velocity increases the bubble size also increases. Protein removal decreases as bubble size increases.

This is why you need a larger diameter skimmer tube to increase the air flow a lot. [/B]

IMO, I think the velocity at which the bubbles exit the airstone have an impact on the skimmer's performance. If one is pushing 1cfm through 5 square inches of bubble producing surface area one's bubbles will have much more velocity than he who is pushing 1cfm through 65 square inches of bubble producing surface area.

IMO, too little bubble producing surface is similar to putting a jet-nozzle onto a garden hose.

I'll e-mail you in a a few days.

Snailman

12/24/2000, 12:29 PM

Originally posted by LiquidShaneo
Oh, thanks for the pix Snailman! That self sealing skimmate collector looks pretty slick! Now I've got another DIY project to work on after the skimmer is complete. My wife is gonna love this... :D

Another question Snailman: how much contact time to you estimate your 5' high skimmers have anyhow?

I looked at the ad for the Waste Collector and thought that it would be a snap to build. :) It turned out to have more fabracation than my skimmer or my dual chamber calcium reactor by a large margin. If you need any help feel free to ask.

I do not have a clue what the contact time is. :(
I did a lot of looking at large diameter pipes and fittings for them last night. :) Large (8" - 10") fittings are very expensive. :( This makes it look like using a PVC tube if I can find one locally or getting an expensive acrylic tube mail order and build all of my flanges out of acrylic. I found a place to mial order large diameter PVC pipe but they wanter you to take a 100' feet of it. :(

I have three heaters in my tank and the sucker cups that they are mounted with keep coming loose. Yesterday's project was to cut a piece of acrylic and drill it for the three heaters. I took the sucker cups off and bolted the heater clamps to the acrylic sheet with nylon bolts. Now they will stay put. :)

[Edited by Snailman on 12-24-2000 at 11:44 AM]

LiquidShaneo

12/24/2000, 10:23 PM

Quote from KW:

I think the velocity at which the bubbles exit the airstone have an impact on the skimmer's performance. If one is pushing 1cfm through 5 square inches of bubble producing surface area one's bubbles will have much more velocity than he who is pushing 1cfm through 65 square inches of bubble producing surface area.

I think you are pretty much just restating what Snailman said in his previous post. If you push a bubble out slowly, you will end up with a finer bubble. If you push a bubble out *fast* you will end up with a larger bubble. A finer bubble will travel up the water column much slower than a large bubble because of friction/buoyancy constraints. This difference in velocity and relative surface area greatly affect the amount of contact time and protein removal from the water column.

Snailman: Yeah, after i got your pix I realized that was probably going to be a pretty involved skimmate collection container. :) I will say this: it certainly looks much prettier than my 1 gal milk jug which I use to currently collect my skimmate. I like the option of having a carbon filter on the skimmate collection container as my wife HATES it when she walks into the den and smells skimmate. I may have to somehow incorporate that option into my collection container...

Oh...my wife almost killed me last weekend when I emptied out my skimmate into the bathroom sink while her parents were over for the weekend. That schidt smelled *nasty*. For some reason she's OK with smelling the cat box but not skimmate... Go figure... :D

Snailman

12/25/2000, 11:20 AM

Originally posted by LiquidShaneo

Snailman: Yeah, after i got your pix I realized that was probably going to be a pretty involved skimmate collection container. :) I will say this: it certainly looks much prettier than my 1 gal milk jug which I use to currently collect my skimmate. I like the option of having a carbon filter on the skimmate collection container as my wife HATES it when she walks into the den and smells skimmate. I may have to somehow incorporate that option into my collection container...

Precision Marine sells the small one for $70 and the large one for $100. If you only need one it may be easier to just buy it. I needed three of them and I already have the tools. I also had scrap acrylic sheet and tube left over from other projects so all I had to buy was the ping pong balls and the plumbing fittings so that is why I DIYed mine. It was great fun also. I know how to make flanges now and that is going to be real handy on the 8 1/2" X 5' skimmer I am planning. :)

[Edited by Snailman on 12-26-2000 at 11:30 AM]

12/26/2000, 12:02 PM

[QUOTE]I think you are pretty much just restating what Snailman said in his previous post.[quote]

No, not really. Snailman's previous post is about the total volume of air in the skimmer and its impact on the velocity at which the air travels through the skimmer i.e. air has less resistance than water. I'm talking about the relationship between the amount of bubble producing surface area and the introduced air.

Obviously, one could never reach the point of diminishing returns, in regard to Chen's study, if one's air diffuser can not handle the volume of air required to achieve this feat. This is where I am coming from. IME, it is quite easy to overpower a wood air diffuser. In fact, after switching from 13 cubic inches of bubble producing surface area to 64.5 cubic inches of bubble producing surface area I realized how little air it takes to overpower a wood air diffuser.

Snailman

12/26/2000, 12:27 PM

KW right on. The subject of the article was the ratio of gas to liquid (air to water) and the total amount of air in the skimmer. P.R. Escobal's fourth skimmer law is "The theoretical volume of air in a skimmer can only be about 13 percent the volume of the skimmer." This is why to really ramp the air volume up you have to up the volume of the skimmer. :)

Fredfish

12/26/2000, 05:23 PM

Slight change of topic. Does anyone know how many airstones I can drive with a Tetra Luft pump? I currently have one 6" airstone hooked up on a 4" diameter 36" Larry Jackson CC skimmer. I am wondering if putting another airstone in the skimmer will up the air volume.

Thanks.
Fred

Snailman

12/26/2000, 07:18 PM

Fredfish... There is more to it than the pump being able to drive the stones. :( You can find this out by hooking the stone up and see what happens. The next issue is the diameter of the bubble tube neck. Most CC skimmers have necks that are to small. Neck diameter limits how much air you can pump into the skimmer before it overflows. What is important is the air/water ratio. If you are pumping all of the air into the skimmer that you can then lower the water feed rate and the efficency of the skimmer will improve.

LiquidShaneo

12/27/2000, 09:11 AM

There's only one way to find out FredFish... lol

I do agree that you need to maximize your bubble producing area of the airstones. I can easily see how you could max it out in a hurry.

KW: is there any way to get a prototype of your airstone? My skimmer is almost done and I'd like to try it out if you would be willing to have another beta tester... :)

liquid

12/27/2000, 10:09 AM

Liquid,

Thanks for the offer. Right now, It's too soon to say. Maybe later

[Edited by KW on 12-27-2000 at 09:17 AM]

12/27/2000, 10:11 AM

Fred,

I used (2) lufts each hooked-up to one 6" diffuser on a 4"x48" skimmer for several years. It did fine.

There are a lot of variables which effect skimming. If you don't enjoy thinking about it, I wouldn't be concerned over it. The major guiding principle is your tank. If all of your animals look great then who cares if your skimmer is running like an old beat-up volkswagon or like a Porche ;)

Fredfish

12/27/2000, 08:14 PM

Snailman. I did all the research (more like reading) a long time ago. The neck on my skimmer is 2.5" (one inch larger than the original design). The diameter choice was one of materials avialable, I just happened to have a 8" piece of 2.5" clear PVC hangin around from another project.

I think my skimmer can handle a more air volume than it currently gets.

I was hoping someone would have some idea what volume of air the Luft puts out in a given period.

I may try using larger thickness airstone (1.5x1.5x6) and see if that gets me more foam.

Liquid. For a change I thought I would ask questions first then fiddle. Foolish me.

KW. Not too worried about the tank, just thinking of ways to improve the skimmer if I should ever need to.

Ironically, with the low bioload in my tank, my live sand bed has shut down the skimmer, so for the moment, skimmer efficiency is a non issue.

Fred.

Snailman

12/27/2000, 08:35 PM

Originally posted by Fredfish
I was hoping someone would have some idea what volume of air the Luft puts out in a given period.

The Aquatic Eco Systems catalog says that the tetra -G Luft Pump puts out .09 CFM @ 1 PSI and .05 CFM @ 3 PSI and that it shuts down at 7.5 PSI. They also say that it will run an air stone in up to 7' of water. HTH

LiquidShaneo

12/27/2000, 10:42 PM

Liquid. For a change I thought I would ask questions first then fiddle. Foolish me.

No reason to get worked up about my comment FredFish...I wasn't flaming you or anything. :/

It's really not all that hard to add a second airstone to your existing setup and as long as you can see into the skimmer body you should be able to make the determination of whether or not a second airstone will help. What it boils down to is that the water column in your skimmer cannot hold anything more than 13% air volume in the form of bubbles. If you see a lot of water voids in your water column right now w/o the second airstone then I'm sure that adding a second airstone will help. You know your setup and your equipment better than we do and you know how it's been running for the last couple of months, so try it and see what happens. No flame intended.

liquid

Fredfish

12/28/2000, 02:01 PM

Snailman. Thanks for the Luft volume info.

Liquid. Didn't mean to sound upset, just don't know how to get smilies into the middle of a post yet :-).

Unfortunately, my skimmer body is not clear so its not that easy to tell if there are water viods.

Fred

SciGuy2

05/11/2001, 12:50 PM

Please forgive me for reviving an old post.

I was going to start a new post asking experiences with DIY CC skimmers and noticed that many design considerations had been already explored in this post. I just didn't want to make people restate things they'd already said. BTW, it is a very informative thread.

I was looking at Beckett, EAP, and HSA skimmers and reallized the catch-22 in these types of designs: to increase the amount of air injection one has to radically increase water flow which in turn decreases contact time.

I noticed that many of you folks were just setting up new CC skimmers in December, 2000 and have had time to evaluate your designs. Do you have any comments/pics for someone following in your footsteps?

I've collected the acrylic, PVC, endcaps, etc. for a 4" diameter 4' CC skimmer and was planning on using the Jackson/Sellinger design. Should I do away with the reducers and narrow throat altogether?

I'm planning on using the skimmer on a 70 gallon system.

Also, I see that Tetra has discontinued the Luft air pump. Is the Tetratec DW96 a suitable substitute?

Thank you very much,
-Lee

Snailman

05/11/2001, 05:53 PM

No problem about dragging up an old DIY post because like this one there is a ton of information. If you would like a nice an easy 4" cc skimmer design emial me and I will reply with the instructions and a drawing.

lkaras

05/11/2001, 06:02 PM

Snailman
I would be interesed also in a good design: lkaras1@yahoo.com
Thanks

SciGuy2

05/12/2001, 11:10 AM

Snailman,

You've got mail. If for some reason you don't get my email my address is : wlmorey@aol.com

Thank you,
-Lee

SciGuy2

05/12/2001, 02:40 PM

Thanks for the instructions, Snailman! I'll be building this puppy this week!

LiquidShaneo

05/13/2001, 12:23 PM

In case you want to see what my DIY CC looks like, here's a couple pix:

http://liquidreef.freeservers.com/equip.htm

hth

liquid

SciGuy2

05/22/2001, 08:59 AM

Looks good, Liquid! Hook 'er up and tell us how she works!

johnny

05/22/2001, 10:30 AM

I personally have never used the old luft pumps, but the DW-96 doesn't seem to get the job done on my 5' CC. I'm probably going to sooner or later have to get another air pump... and I still have to try KW's air diffuser (so much to do, so little time).

Nick

SciGuy2

05/22/2001, 12:10 PM

That's disappointing. I just got a DW96 last week. The way things are around here it will be 2-3 weeks before I can finish the skimmer. I'll be bummed if the pump won't drive it.

GROSSR

05/26/2001, 11:12 AM

I have an 18" tall and 4" column CC. Just bought a new TetraTec DW24-2. Both outlets connected to a Coralife Limewood differsor. I couldn't get skimmate out of this pump if I purchased from the LFS and put it in the skimmer. I too would like to know if the DW96 could do the job?

05/29/2001, 01:32 AM

Hi,
I use a 96-2 on my 4" by 4foot skimmer. It works really well, and is quiet. I added a T to the airline with a small needle vale, so I can let some air out of the line when i put a new airstone in. With 2 new 3 inch airstones I have to cut the air volume down a bit for the fist day or two, otherwise it will over flow. That is with, and I am guessing here, a 50 gallon per hour flow.
jason

Rowdy

05/29/2001, 05:37 AM

What do you think would happen if I incorporate this new Beckett foaming fountain head I got at HD for $10 into my Ron's Saltwater Heaven CC skimmer? I was thinking of enclosing the beckett inside of the skimmer body facing downward and taking the .5" barb fittinf off, tooling a straight pvc shank through the body, and barbing each side (somehow) then running nylon tubing or similar to the beckett and to the feed pump. I dunno, might overpower the skimmer. I guess I could re-tool the body. There is no urgency though, my Ron's CC works awesome.. maybe too well for some folks opinion. The skimmate that thing produces will gag a maggot!! WOW! it's bad. Ideas?

SciGuy2

06/13/2001, 04:19 PM

Alrighty. The skimmer is 95% done and I'm gonna test it out this weekend (I hope).

One last question before I glue it all together: what should the water level be relative to the neck of the skimmer? I was thinking about trying it something like 2-3" below the neck.

Thanks,
-Lee

06/13/2001, 05:10 PM

Use a compression coupling or union to adjust the level of water. I'm starting mine about 1" below the neck then I'll adjust (cut it rather than try to put back) when it's running.

pmui

06/14/2001, 12:44 PM

snailman,

got mail

SciGuy2

07/05/2001, 05:41 PM

Snailman,

Just wanted to jot off a quick note of thanks.

I've had my CC Skimmer (based on yours and Joseph Sellinger's plans) running for the the last 2 weeks.

I'm very happy with it. It produces about 1/4 to 1/2 cup of skimmate with a pea-soup color/consistancy per week, which is quite a lot for a light to moderately feed 70 gallon system.

The effluent skimmate bubbles are almost identical to those pictured on your website.

The only major change I had to make was to reduce the length of the bubble neck from 6" to 2" and run the water level in the skimmer slightly higher than in your instructions. This is most likely due to the fact that I'm running a much smaller air pump than you are (Tetra DW-96).

Thanks to everyone for their input on this thread ( LiquidShaneo, and KW, especially)

Thanks again,
-Lee

P.S. Snailman, you have one of the sharpest, cleanest reef websites out there!

thunt

02/06/2002, 10:55 AM

I've been reading this old thread and used it to assist in building my CC skimmer.

A lot of posts mention having a higher air to water ratio. I'm using about 400 lph air and 140 lph water.

Now, 2 German companies who have produced skimmers for years, Sander and Aquamedic, both still produce CC skimmers.

Aquamedic make a Turboflotor 5000 (48" tall and 78") and there quoted flow rates are: the waterflow should be between 1500 and 3000 l/h, the airflow between 500 and 750 l.

Sanders make a skimmer and there quoted rates are 600lph water and 300lph air.

Now the principle of having a slower flow rate makes sense to me, but why would a "professional" company, presumably with qualified designers have come up with more water than air?

One thought I had was that if the water was flowing down through the air faster, then perhaps it slows the speed the air can rise to the top and keeps it in suspension longer?

Have a look at the aquamedic link for the Turboflotor 5000 Aquamedic link (http://www.aqua-medic.de/cgi-bin/php/display_product.php3?cat_id=9&lang=en&pos=4)

It doesn't look much different from our DIY ones (a bit more polished perhaps!). One input, 2 outputs, bottom drain tap, 2 airstones, etc.

So, whats your views on the flow rate issue. I thought I had it clear in my mind until now.

I've used a small Sanders for years and was very impressed. So have respect for both Aquamedic and Sanders. I figure they know what they're doing better than me.

Regards

Tim Hunt

Sebastian

02/06/2002, 09:56 PM

Just to change things up a bit, Has anyone used the overflow to feed the CC skimmer input? I havent used the L Jackson sytle skimmer but have often thought of using it in combination with the Durso standpipe modification as the feed line. I am unsure if the flow rate would stay constant or if this would have any effect on the skimmer output at all. If this is possible it would eliminate an additional pump for the skimmer.

smillin920

02/07/2002, 11:56 AM

What is everyone using for airstones, and where do you buy them? I am about to build one of snailmans 6" cc's, and am going to us a Tetra Tec DW 96-2. Any suggestions on setup or supplies is appreciated.

Thanks in advance for any replies,

Shawn

Snailman

02/07/2002, 09:23 PM

smillin920

[welcome]

You can find wooden airstones at most online and offline LFS or you can make your own.

kstockman

02/08/2002, 04:31 PM

Sebastian

The only way to go. I fed my 4" OD 7 ft tall CC skimmer from the overflow (check out my web page in the DIY section for plumbing). I had a basement sump. Now I have to use a pump to run the skimmer because I don't have enough drop. I used to run everything possible off gravity feed. Now it is only the Ca reactor. I had no flucuaction in the flow rate because the way that I plumbed it. I would adjust the water flow with a ball valve and the extra water went through a bypass line directly to the sump

I was thinking about putting dual 6" OD 5' tall skimmers on my 300--one off each overflow. I am planning on having the skimmer effluent from one or both of the skimmers go to a grow out tank.

kstockman

02/08/2002, 04:40 PM

I have noticed that when I reduced the water flow on my skimmer (no gravity and only a small mag pump), that I get extremely dry foam and that I have no stink. I think that this is a bad thing. I plan on increasing the flow (new pump or use of gravity feed) to get wetter foam. I like a to collect about 1 gallon of skimmate a week. WHen I had the skimmer operating this way, the stuff smelled so bad it would smell up the entire house for an hour.

I have found it easier and cheaper to build a collection cup that is square. This way you don't have to buy an expensive large diameter section of acrylic. I also make the collection volume large (on the order of a half gallon)

LiquidShaneo

I have a 3" OD skimmer from Ron's Saltwater heaven that I am thinking about getting rid of. It is not in service and may not go into service once I build a 6" skimmer. It is about 3 years old.

LiquidShaneo

02/08/2002, 04:46 PM

I thought I'd throw this out for reference since I was just looking at the webpage when you posted again Ken:

http://home.att.net/~rstockman/newpage13.htm

It's a neat idea and if I ever had a sump in the basement and a tank on a second floor I'd definitely look into this design. :)

Thanks for the offer Ken. :) However, since the inception of this thread (back in 2000) I have built my own CC skimmer based on conversations w/ Snailman and reading thru PR Escobal. Here's what mine looks like today:

http://www.liquidreef.com/equip/diy_skimmer/diyskimmer_cat.html

So far it's not in use but more than likely it will be used on an up and coming system that I'm working on right now. If we hadn't had this ice storm and hadn't had to invest in a #$% generator, I would be much further along on it than I am right now. Oh well, at least I now have a generator for future power outtages. :)

Shane

kstockman

02/08/2002, 05:35 PM

Nice job on the skimmer. Here are some things to consider about the skimmer. If you have considered them, then just ignore this post.

1. put a close off valve on the collection cup. If you have too much water flow and airflow you can flood the system and collect water at a very rapid rate in the collection cup. If the collection cup is closed then the water will go back into the system. If not then the water will leave the system and this is bad.

2. Consider a clear pipe for the small diameter pipe, just so you can see what is going one as far as bubbles are concerned.

3. Consider cutting a viewer into the collection cup so you can see if it is full. Cutting out a 1/2" wide hole then glue in a piece of acrylic. Then again once the thing really gets going, you usually can't see anything in the collection cup anyway.

Just some thoughts

LiquidShaneo

02/08/2002, 06:52 PM

Thanks for the tips, Ken. :)

1) Yup, was planning on making this mod after my BakPak w/ the same mod emptied out onto my floor while I was at work. It didn't smell pretty when I got home and found that as you can imagine. :p

2) Have also considered that as well as after I made it I realized it was going to be a PITA to see what's going on in there. I'll grab some spare clear acrylic/PVC to fix that somtime. :)

3) Also have considered this as well. I do need to be able to see in there to see what's going on. Heh, I might just end up rebuilding the collection cup using your idea of a square cup so I don't have to get in the acrylic. :)

Shane

thunt

02/09/2002, 06:47 PM

Any feedback on my above questions about flow rate?

Tim

Snailman

02/09/2002, 11:20 PM

Originally posted by thunt
Any feedback on my above questions about flow rate?

Tim

Get a copy of Aquatics Systems Engineering by P R Escobal ($21 Amazon) and run the formulas yourself and you will understand all you want to about flowrate. :)

thunt

02/11/2002, 12:06 PM

I could buy the book ($109.85 to us here in the UK!) but I'm not so much interested in the formulas, but the reason why 2 large skimmer manufacturers would use higher water flow than air. Most of this thread favours more air than water.

I presume a skimmer manufacturer would have access to the the same formulas, so was inquisitive as to why they would have chosen their approach.

If anyone can throw any light on this I'd be greatful.

Really don't want to spend that much on a book to clear one point.

Tim

LiquidShaneo

02/11/2002, 12:10 PM

Heh, you know that's a very good question. :) To me, it's obvious that they either do not understand the physics of it or they have chosen to not use the physics. I tend to believe the latter. :D

Shane

Aaron Shelley

02/11/2002, 12:58 PM

All this talk about counter current skimmers with air stones being the only way to independently control the air:water ratio has me confused.

Why can't you have your venturi or needle wheel pump on a dedicated loop and run your water through the skimmer with a different pump(or gravity feed for that matter). Now you can precisely control both air and water and never replace an airstone.

Your number of devices is the same, you just trade an air pump for a dedicated venturi or needle wheel pump. Sure some air pumps are cheaper than some of the pumps necessary to operate a venturi or needle wheel, but to get lots of air on a big system (mine is over 600 gal) you need a powerful air pump and a large reaction chamber. It seems the cost would be the same.

I'll admit that I've been using a needle wheel system for about a year now and like still:D

LiquidShaneo

02/11/2002, 01:48 PM

While that will work, you will also significantly increase the turbulence inside the skimmer body as compared to a CC skimmer run by an airstone and one pump. According to Escobal, you want slow counter current flow with minimal turbulence for maximum efficiency.

FWIW, I believe Aquatic Technology sells a skimmer similar to this if I remember right...

Shane

NYReefMan

02/11/2002, 03:34 PM

kstockman, liquid, etc...

I understand 2 out of the 3 mods you were talking about, but
how and where exactly would you install the close off valve on the collection cup?

NYReefMan

Snailman

02/11/2002, 09:31 PM

Originally posted by Aaron Shelley
All this talk about counter current skimmers with air stones being the only way to independently control the air:water ratio has me confused.

Why can't you have your venturi or needle wheel pump on a dedicated loop and run your water through the skimmer with a different pump(or gravity feed for that matter). Now you can precisely control both air and water and never replace an airstone.

If you can find a way to get a venturi to put out as much air as you want at any water flow rate your should patent it. :D The same goes for the needle wheel. The air and water are tied together, if you want more air you have to add more water which does not change the ratio.

Snailman

02/11/2002, 09:33 PM

Originally posted by thunt
I could buy the book ($109.85 to us here in the UK!)

Why is it five times as much in the UK?

thunt

02/12/2002, 03:46 AM

No idea Snailman. Have a look on Amazon.co.uk and thats the price that comes up.

Seems we get stung a lot on aquatic stuff.

For example, a bought an Amiracle PS3 skimmer over here and it cost me $150. On a visit to the US after I saw it MO for $39.95. Sold the PS3 now and made my own, but gives an example of pricing issues.

Tim

SciGuy2

02/12/2002, 09:24 AM

Liquid,

It seems to me that we have been quick to dismiss recirculating venturi designs. If properly designed with a lower box section where the turbulance is contained, and possibly baffles to further isolate the skimmer body from the turbulance of the recirc. intake/output, a recirc. venturi skimmer should work well.

The quality of bubble size would continue to be a problem, air diffusers simply make the most consistant bubbles. However most diffusers only work well for 4- 6 weeks so I persist in being interested in venturi designs.

I'm working on making some small venturi tubes right now, trying to make a smaller Beckett assembly. After I get one that I like I plan on tinkering with a recirc. venturi modification on my snailman skimmer to see how it compares in quality and ease of maintenance.

-Sci