How to test skimmer efficiency?

[DennisRB]

How can you gage how efficient any given skimmer is at removing waste? Is there some sort of test that gives an indication to how well it works? I made a larger CC skimmer and would like to know how it stacks up against some of the other types of skimmers.

[CaptiveReef]

What makes a skimmer is the actual contact time. The larger the skimmer the more contact time the water will have with the bubbles. What I mean is the taller the skimmer is, will allow you to increase the water flow through the skimmer, and also allow for increased air introduction.
When you put water through a tube, and add air the water height in the tube rises, you have to allow for that increase in water height when you are designing a skimmer.
With shorter skimmers you have a decreased water flow, but an increase in air introduction, so the water is exposed to maximum contact, The counter current skimmer design allows for water flow to go down and goes against the bubbles going up.
The skimmer diameter, and height dictates the flow rate and the amount of air introduction, having a skimmer with valves for air and water allow for finer adjustments.
There are some opinions on the actual quality of skimmate that is produced from a skimmer. Some like it wet, some prefer a more dry foam. Myself I prefer the dark tea colored skimmate.
Some opinions are that a skimmer should not be run all the time, I keep mine on 24/7.
I built a 6ft skimmer, it is 4inch dia PVC counter current. The maximum flow rate of water through it is 400 GPH. The air is introduced by a Venturi valve that is positioned a little below the half way mark on the skimmer.
If I go more than 400 GPH there is no skimmate produced, when I bring the flow down to the 400 rate, it becomes a foam factory.
Also if you introduce foods to the tank that contain high carbohydrates or fats the skimmer will go into major foam production, the skimmer will use these to bind waste in the water and produce a ton of foam.
Add a little Stress coat to a tank with a skimmer and watch the fun begin!!!!!!!!!!!! Don't do it your skimmer will empty your tank from the amount of wet foam that is produced!!!!!!!!!!!
It's better to go with increased flow rates on air/water and tune them down to get the performance you are looking for.


:D CaptiveReef

[DennisRB]

Thanks. Mt skimmer is 4 foot tall and 6" wide. I use a 20 liter per minute air pump with 8 wooden air stones. I also use around 400GPH through it. My tank and sump is around 200G. Would you say that my tank is heavily skimmed?

I have noticed that my skimmer goes rank when I add food to the water. I have to be careful that it does not drain too much water when I feed. What size is the foam outlet riser on your skimmer?

[CaptiveReef]

4ft tall 6inch dia is a great size skimmer!!! The 400 gph with the 8 air diffusers will provide you with plenty of air for air/water contact time. Your skimmer design reminds me of Daniel Knops skimmer design, He uses a round manifold to supply air to 6-8 limewood air diffusers at the bottom of his skimmer tube.
My foam outlet riser is 6 inches tall and 2 inches wide, clear acrylic.
At the top of the riser there is a 1/2 inch tube with a barbed elbow, I have a tube going from the elbow to a bucket.
You are not over skimming your system, A fully stocked reef tank needs to have a good skimmer. All corals produce Terpens which is their own personal chemical defense, skimmers remove these Terpens at a rapid rate. These Terpens can effect other less aggressive corals, and even slow down their growth or even kill them.
The life in the tank can only utilize so much waste, the excess has to be removed, and skimming provides this form of waste removal.
Also there is a large amount of oxygen that is addded to a tank with the use of a skimmer.
That is why it is said "Get the largest skimmer you can afford"



:D CaptiveReef

[DennisRB]

You can see my skimmer here .skimmer (http://archive.reefcentral.com/forums/showthread.php?s=&threadid=378619)

The outlet is 4" and I have trouble getting a decent foam consistency. I have some clear acrylic to make a better riser, the piece for the small riser is about 1 2/3 wide do you think it would be big enough? Just after another opinion

Is there a formula or rule to figuring this out?

[CaptiveReef]

Kgross suggestion sounds like the best for your design, keep the existing riser, and just add the reducer, that will work. Also you may want to add a valve to the water supply line to see if you reduce some flow you may get better foam production, reduce the flow slowly, and see how the skimmer reacts.
The skimmer is a nice design!!



:D CaptiveReef

[CaptiveReef]

This is the skimmer I'm using to run my coral system.

[CaptiveReef]

closeup

[CaptiveReef]

skimmer pic

[DennisRB]

Thats a monster :eek1: Good job :cool:

I got some 6" lengths of clear acrylic and I want to use them so I can see the foam. I wanted to use one 6" long 4" diameter out of the existing 4" reducer then just connect the 1 1/3 piece to that as the final riser. If if you get me?

Will the skimmer efficiency be affected if I connect the 1 1/3 piece straight to the 4" piece via a flat piece of acrylic? As opposed to using a tapered reducer. I mean just glue a flat piece on top of the 4" piece then cut a 1 1/3 hole in it and join the 1 1/3 piece on. The 4" and 1 1/3 lengths are both 6" long, is that a good length?


Like this.
__
i i
i i Clear 1 1/3
__i_ i__
i i
i i
i i Clear 4"
i_____ i
i \
i \ Exiting reducer.
i________\
i i
i i
i i
i i

[DennisRB]

Well that drawing didn't turn out the way a drew it. You might be able to visualize what I meant by it.

[wasp]

Well CaptiveReef that's the meanest, rudest looking skimmer I have ever seen.
Congrats on building something like that. Is it venturi powered or what?
Bet that skimmer won't let any crud stay in the water.

[CaptiveReef]

Thanks wasp it is Venturi driven, with added water flow. It pulls alot of waste out of the water. My next question is where are my links to my skimmer pics?

:D CaptiveReef

[CaptiveReef]

Originally posted by DennisRB
Thats a monster :eek1: Good job :cool:

I got some 6" lengths of clear acrylic and I want to use them so I can see the foam. I wanted to use one 6" long 4" diameter out of the existing 4" reducer then just connect the 1 1/3 piece to that as the final riser. If if you get me?

Will the skimmer efficiency be affected if I connect the 1 1/3 piece straight to the 4" piece via a flat piece of acrylic? As opposed to using a tapered reducer. I mean just glue a flat piece on top of the 4" piece then cut a 1 1/3 hole in it and join the 1 1/3 piece on. The 4" and 1 1/3 lengths are both 6" long, is that a good length?


Like this.
__
i i
i i Clear 1 1/3
__i_ i__
i i
i i
i i Clear 4"
i_____ i
i \
i \ Exiting reducer.
i________\
i i
i i
i i
i i
Dennis can you draw it freehand, so I can get a better understanding of what you want to do.


Thanks Greg

:D CaptiveReef

[DennisRB]

This is it before http://members.optusnet.com.au/~cimber1/mypic6.JPG

http://members.optusnet.com.au/~cimber1/mypic7.JPG

I didn't get a a pic of it all together but if you imagine the old cup gone and this in its place.

Basically the whole clear section is full of foam with large bubbles.

http://members.optusnet.com.au/~cimber1/mypic11.JPG

http://members.optusnet.com.au/~cimber1/mypic12.JPG

Sorry, my camera is very crap.

The level is still hard to adjust if I go to high it just overflows and the skimmate almost looks like clean water. How it is now, it will bubble away and every few seconds a big wad of foam will come out. What should the skimmate look like? How much should I be aiming to get out per day with a 190G system?

[CaptiveReef]

That is pefect!!!!! the skimmate looks great. From your description and the photos, it looks like you have it dialed in just right.
As you said when the level is to high you get very wet foam almost total water, you don't want that.
You want the wads of foam, and as your pictures shows your skimmer is working properly the skimmate is dark in color. Depending on your waste levels in your system, your skimmer will remove this waste on a constant level.
To keep the skimmer working properly keep the clear section clean, in the pictures you can see build up already,(which means the skimmer is already working properly).
It's hard to say how much skimmate a skimmer will produce, again it goes with stocking levels, how much life, and what your feeding your tank.
Keep your skimmer dialed in as you have it. The skimmer is removing waste as the photo's are showing. With it being run 24/7 and cleaning the clear section of the thick dark waste buildup, which will start to coat the walls. Keep an eye on the wood airstones as they will start to clog causing the bubbles to get bigger, this will effect the skimmer's efficiency then they will need to be changed. You usually get about a month's life out of them.
You have built yourself a great skimmer which will keep your system clean. 190 gallon system, with a skimmer that size you have skimming well covered!!!
I use skimming and carbon together, to keep my water crystal clear.
Water changes are a must, I never liked to do them. I have found with my 90 gallon tank, a one gallon a week water change does the job, I add buffer to the new water then the salt. It does the job of replacing all the needed trace elements, now I'm not juggling all the trace element bottles, and it's alot cheaper just to buy salt. I also add Kalkwasser for extra calcium.
I do the same for the 600 gallon system, but it's 5 gallons a week.

Please keep posting on the skimmer performance.


Thanks Greg


:D CaptiveReef

[DennisRB]

Thanks. The skimmate looks like a light tea color and is watery. The top pic is more representative of the color because the bottom pic is taken without the flash and makes it look darker. How much of this should I be aiming to take out per day/week? ATM I am getting about 1.5 pints a day. Is that too much for a 190G? ATM the tank has nothing in it but sand and a few toad fish for cycling. I feed 2x 1/2" cubes of meat per day. I think the air stones are starting to produce large bubbles too.

[jdieck]

The only one measurement of a skimmer's efficiency will be the level of ORP in your water created by the skimmer alone.
If you want to compare try to keep your usuall parameters and feeding schedule and run each skimmer for a week and take ORP reading and compare both.

[DennisRB]

Cool. You would have to cross reference it with the amount of skimmate produced though wouln't you?

Whats the best way to measure ORP?

[jdieck]

Not really as the amount will be dependant on the concentration, Large amount of light colored skimmate may contain same amount of stuff than a smaller amount of darker thiker skimmate.

Measuring ORP is usually with an electronic monitor. The aquarium ones might not be as precise but cpould provide a general reference if the probe is cleaned and calibrated regularly.
So unless getting a more expensive sophisticated meter the measurement will be at best qualitative rather than quantitative.

[DennisRB]

You would have to cross reference it with the amount of skimmate produced though wouln't you?

"Not really as the amount will be dependant on the concentration, Large amount of light colored skimmate may contain same amount of stuff than a smaller amount of darker thicker skimmate."

OK, now I am confused. Doesnt't what you just said demonstrate that you do need to compare it to the amount of skimmate produced for the very reason you mentioned?

How much do these ORP probes cost? So far I have never thought of getting one.

[jdieck]

The skimmate concentration will be very difficult to measure so you would not really know if the skimmer producing more skimmate will in reallity be removing more contaminants. This si why you need to measure the quality of the aquarium water and not the amount or quality of the skimmate.

The ORP (Oxydation Reduction Potential) is a measurement of the oxidative or reductive capacity of the aquarium water and it is associated with water quality. A low ORP denotes much organic and reductive chemicals in the water which will reflect a low performance of an skimate as many of these are the mere compunds it is suppose to remove. The lower organics (Proteinaceous matter) in the water, the better the skimmer performance and the higher the ORP reading will be.

An ORP monitor starts in $100.00 dollar level and up to the $1000.00 level for lab grade equipment.

Pin-Point, Hana and other similar brands have aquarium versions of ORP monitors and ORP controllers. The controllers are popular to monitor and control addition of Ozone. As it increases ORP it has to be limites as ORPS higher than 450 mv (millivolts) are as dangerous in an aquarium as ORPs below the 250. ORP is maintained above 650 mv for potable water sterilization and for water treatment.

[DennisRB]

"The only one measurement of a skimmer's efficiency will be the level of ORP in your water created by the skimmer alone."

"This si why you need to measure the quality of the aquarium water and not the amount or quality of the skimmate."

So I read that first bit wrong, and you only ever meant to measure the aquarium water? That makes sense. However ORP seems to be a bit of a debated topic on how useful it really is under normal conditions???

[jdieck]

Most of the controversy stems from not knowing which kind of reactions are happening and which kind of chemicals are involved so there is no agreement if an ORP of 375 is better than an ORP of 325 as the 325 measurment may include substances that are good (specially for feeding filter feeders) although most will agree that a sudden change is an indication of something going wack and that too low of an ORP (Below around 280) or too high of an ORP (400 +) is detrimental.
The second controversy stems from wether the monitors we use are precise enough. Before and after cleaning the probe they can drift as much as 80 mv and take two to siz hours to stabilize.

The first part may not be a problem for the test as there is agreement that a higher ORP is indication of cleaner water wether "cleaner" is better for your aquarium may not play a role for testing purposes as you will still know which skimmer cleans it better.
For the second one it is more problematic, besides using a good quality monitor with calibrated and stabilized probes before each test you may need to set more than one monitor in different points of the aquarium and run statistics to validate the results and minimize the measurement error. This is why I mention you may be able to trust qualitatively the change itself (Small, medium or a large change in quality) versus the quantitative measurement itself (a difference of 20 vs 50 vs 100 mv).

If we would like more scientific data then we might have to set up control procedures and use a tank whose impurities are artificially controlled and known then the variability of operating in such a variable environment as an aquarium could be can be taken out of the test.

All this is to say that it will not be perfect but will be better than other potential measurements.

[CaptiveReef]

The measure of the Redox/Orp will also show how good the skimmer is working. As jdieck has said the higher level Orp will indicate that the skimmer is doing the job, the more waste or even a death in the tank will show in a drop in Orp levels.


:D CaptiveReef

[A.K.A. ReefDoctor]

You can always drop an ounce or two of "Stress Coat" into the pump the feeds the skimmer. That will make the skimmer go crazy producing foam skimmate. That should tell you weather your skimmer can work well.
Or you can Read the skimmer chapter In P.R. Escobals book..
"Aquatic Systems Engineering"
ISBN # 1-888381-05-1

[AquariaUSA]

I took the skimmer off my personal tank (200 Oceanic with about 175-225 gallon in sumps, etc.) last August '03 and have not really missed it all that much. I also took the reactor off prior to that. However, the water sure does have a yellower tinge :) Go sponges!

[jdieck]

How is your ORP? How Size Fuge?

[AquariaUSA]

I keep meaning to put a monitor on the tank to check for I frequently overload the entire system.

The main display is a 200 Oceanic. The sump is a 125 AGA with two sets of baffles (first drain area from tank has eggcrate and several sponges, tunicates, etc.). Second area is 4" DSB fuge with a little rock, sponges, and tunicates. Third area is reservoir before pumps return water to tanks. Two AGA 40 breeders are inline and originally meant for coral frags and clams. Three 10 gallons hold shrimp pairs and some polyps. A few months ago I added another AGA 125 gallon to house Aqua-Cultured SPS until we install the SPS system in our warehouse. The main tank is loaded with corals and fish (Lopez tang, purple tang, naso tang, hippo tang, sailfin tang, yellow tang, clowns, sixline wrasse, rock blenny, sump has bird wrasse & falco hawk, top 40B has scooter blenny, rainfords goby, clown...125 has 8" volitan lion, 7" miniatus grouper and anywhere from 40-100 sps depending on whats in stock. I know the ORP goes through swings depending on when I do a waterchange (+/- 40 gallons) with heavily aerated water, but so far so good. Had the occasional cyano/detritus pop up, but nothing more than a small patch here or there. KH frequently does drop down to 6-7 dkh without the reactor, but most wild colony sps have been unaffected. Temps slide from 76-84 depending on the week (have chiller, did not want to use it either :)

[jdieck]

Now I know why you said Go Sponges! :>)