Skimmer production
 

Hi Anthony!

Have followed your writings and advice for several years now and have
learned much! (I read much, post little). I do have one question that has always confounded me in regards to your suggestion that skimmers should be able to produce a full cup of dark skimmate each day. :eek1:

Could you please explain the assumptions used to determine this recommendation?

I currently run a Euro CS6-2 on a 125 with 50 gallon sump, but have never been able to attain anything near a full cup of dark skimmate per day.

Thanks, Jim

I have a very similar question that I was going to post else where but will ask it here since it seems similar.

When you say a CUP of skimmate, do you mean a "CUP" in measurement terms, like for cooking...i.e."a cup of milk"? Or do you just mean one collection cup full, whatever that may ammount to? Also like he asked...what is the controll for this reasoning. Is this based on the average 100g tank...55g tank...30g tank? I have a 37 and a 30 and have never been able to get a full cup of the dark stuff no matter what I do...but I'm not assuming that the tank is clean. I would think that a 10g nano reef would not produce a good cup a day or maybe even every 2 to 3 days. But is that becasue it is smaller and has a lower bio load....

Every time I read you saying that you are dissapointed by people that cannot produce this one cup minimum I get a little discouraged and think..."anthony (my hero:D) is mad at me again. Like your talking just to me. I realize that a lot of us don't mess with the thing near enough but when we do nothing changes anyways...

help.

dave

heehee... very good/fair question my friends. :)

ya, know... its a funny thing too. I remember reefing in the 80's early days and thought I had a pretty good system going. I was smart enough to "know what I knew"... but not yet smart enough to "know what I didn't know." (a fab Fennerism). Time and life have opened my eyes to so many wonderful things, and (thankfully!) brought more humility along with that!

Daily skimmate production is an ideal that anyone can reach, presuming you want to use protein skimming as your primary means of (aggressive) nutrient export. There are of course many ways to run a healthy system with less skimming or no skimming at all. But that’s not what we are chatting about here.

I was a marine aquarist already for more than a few years and had heard other experienced folks harping the same thing... daily skimmate, daily skimmate, daily skimmate! It was quite the push back then in "berlin style" reef days where the conscious attempt was to have a nutrient starved reef. It hadn't quite sunk in to us yet that reefs are not nutrient barren, but rather nutrient banked. All tied up in living mass that is rapidly converted/recycled, etc.

but I digress...

It was only when I leapt from basement farming (some basement... my 3K gallon discus hatchery :D) to commercial activity (the greenhouse) that I really paid careful attention to hardware installations and maintenance. It was no longer a hobby anymore, but instead I had big money riding on the line ;)

I had no intention of failing either with GH... to do so would mean that I'd have to get a real job someday. Perish the thought! But I digress... again :)

So with daily and systematic neuroticism, I micromanaged my greenhouse and made my skimmers (actually 6' DIY Nilsen style skimmers) work optimally. And what I saw happen was that in 240 gall tanks (20X)... most with single coral species... many getting no feeding at all (nearly fully autotrophic Xeniids, Briareum, etc)... and literally no fishes or only one per 240 gall (a copperband here for Sycon control... dragonet over there for acoel flatworms, etc)... I still got full cups of daily (coffee) dark skimmate! Simply amazing to see. And really just a matter of the gastropods grazing their daily diatom growth, and good water flow keeping their fecal pellets in suspension. Daily faithful supplementation (iodine, Vita-chem, Selcon) no doubt helped the diatoms continue to grow ;) But my net daily import of nutrients was very small compared to what most folks today keep as fish and corals loads, feedings going in, sub par water flow in home aquariums, etc.

So I’m now converted... harping to you like those kind, mother hen experienced aquarists that harped at me.

When you see a 240 gallon tank that gets no food, has no fishes, monospecific for Xenia, and only dry sand and dry rock for substrates (no LR or LS for fear of bringing in pests, predators or nuisance algae)... and the tank still yields 4-8 oz of coffee dark skimmate (!), you'd be converted too. :D

So... why don’t you get such daily skimmate? There are many common reasons for this.

The number one reason is the quality of water delivered to the skimmer.

Anything less than raw water overflowed straight into the skimmer is a compromise.

Hence the popularity and track record of Tunze rail- and top mount skimmers (they sit at the surface of the water).

I understand that this is not always practical. Top mount skimmers are unsightly, and not everyone can or wants to plumb their overflow directly into the skimmer instead.

So what’s the next best thing? Well... overflowing raw water into a narrow and concentrated skimmer vessel (just slightly larger than the footprint of your sump model skimmer... or really... just the pump that feeds the skimmer). The easiest way to accomplish this is to seal a partition in the sump if the sump is large enough. Else, just get a small plastic or glass vessel (again... just large enough to squeak the skimmer into) and drill it to overflow into the sump. It will, of course, be kept next to and slightly higher than the sump for this strategic position between the overflow and the sump proper.

If instead you simply sit your skimmer in an open sump... you may just want to unplug it and save the electricity. ;) I'm guessing you get a full cup of skimmate out of that skimmer once weekly or less. It’s no great surprise. Some skimmers can perform well this way... but most do not. And it’s as much to do with size (small) and flow (high) of the sump that makes skimmers in open sumps work at all.

The problem with the majority of skimmers installed (and working poorly) in open sumps is that the fluctuation in water level (turbulence and/or evaporation) slightly affects the head (pressure) on the pump and in turn the amount of water forced into the skimmer. The open sump with slower flow also wreaks havoc on the collection/concentration of proteins (they can migrate back to the surface of the water as they do in the main tank) above the level of the skimmer pump in this case.

That reminds me of the problem with HOB skimmers... their feed pump is drawing water from several inches below the surface of the tank. Wanna improve HOB skimmer performace? Raise the powerhead as close to the surface as you can. Its not as good as getting overflow water (better concentration of surface protein overflow water)... but it is a huge help.

Back to those sump model skimmers... if you cannot seal a partition into your sump... and if you cannot fit a skimmer tank next to or above the sump... then stick the skimmer in a bucket in the sump so that it sticks up above the active running sump water level. Feed this bucket with (again) raw water from the display above, and simply let it overflow the sides of the bucket into the sump proper.

Another big design flaw of skimmers... poor exit control of water. Better skimmers have a gate valve (not a ball valve) for fine control and adjustments. Poor skimmers need one.

Maintenance: some organic/colloidal matter needs to build up (0-12 hours) on the inside of the neck to help skimmate climb... but after 2-3 days, it actually impedes skimmate collection.Clean your skimmer neck interior every couple of days for overall improved skimmate collection. Having two skimmers cleaned on alternate days for big tanks is particularly helpful.

Shall I go on? ;)

Skimmer design. Sigh... we/I could talk for days about this. You'd think that if you spend $200+ dollars for a skimmer (even 300-500) you should get a wicked good performer, right? Well... one would think so. Alas, this is one area of the industry where the adage "good things are seldom cheap and cheap things are seldom" good actually doesn’t hold up. I would not take the majority of skimmers on the market for free.

Fortunately... on message boards like this with a lot of skilled aquarists, it’s not hard to see/read (archives) recommendations for quite a few good performing skimmers. My only beef with some of the better skimmers is that they are poor values (weak bang for the buck... or in otherwords: overengineered/overpriced).

Will you get twice the skimmate production/quantity out of the best $800 skimmer as you will out of the best $400 skimmer. Nope... not even close. There are some fab skimmers for $200-400... and I have yet to see a skimmer over $500 that was a good value.

Last of all... there is just daily tweaking and tuning and learning your skimmer. That is something we need to see more of... workshops at local clubs showing people how to install and maintain their skimmers. Dialing needle (air) valves on venturis (boosting the air injection)... showing the difference (benefit) of a gate valve on the outflow versus the inflow side.

I do hope I've given you some food for thought though.

FWIW... the best skimmers I've even used (total skimmate volume/quality) were those DIY Nilsen style skimmers. But admittedly, they are large, ugly, noisy and more (daily) work to keep going.

Nowadays... I am quite content with an ASM, Euro-Reef, or Aqua C skimmer. There are plenty of other great skimmers out there. I just figured I'd save somebody the keystrokes to type what brands I thought were good values :D

with kind regards to all,

Anthony

other things to improve skimmate production... the internal horizontal overflow (do a keyword search or peep the illustration in my Book of Coral Propagation). Instead of having 2, 3 or more holes (back wall drilled tanks) directly drawing say the top half inch of water off the surface (or worse! those awful internal towers with floor drilled holes where all water overflows a narrow weir)... the long horizontal overflow stretches that same flow out over the length of the dam... allowing you to capture "thinner" surface water that is more concentrated (proteins).

Also... bubble size and air flow is everything. Most skimmers can tolerate a wide range of water flow, but few do well with weak airflow or large bubble size. Some skimmers can be boosted by adding a strong pressure rated airpump. Or... cheap venturi valves can be improved by adding a precison needle (air) valve to the intake.

FWIW :)

Thanks for the informative lesson - an excellent read. You should sticky it! :)

Edit: FWIW to anyone wanting more great info from Anthony, I highly recommend his book - learned tons from it!

Should one avoid aiming the outlet of powerheads to the surface?
Myself, and many others, like to have much water movement on the surface to get more "life" in the light. Do you think we would get more efficient skimming if the surface was more stable/quiet?

Vidar

very good point, Vidar

indeed there is some finesse to be had here. We don't want a glass calm surface... but indeed if it is choppy, all bets are off on optimal skimmer production. The point may be moot though if you are simply willing to shift (more) towards another means of nutrient export. So... if you favor the action at the surface, compensate with more water changes for nutrient control... and/or a brisk chaetomorpha refugium/vegetable filter.

But if you want to get your money's worth out of the skimmer, I do feel it would be better to not focus action/flow at the surface.

Noticed the times on a couple of those replies were in the wee hours!
Do you sleep:o ?!

Thanks for the "food for thought". Looks like I may have to tweak a few items in my setup to insure efficient operation of the skimmer, and you have generously given me more to consider!

Jim

ahhh... a night owl writing when its quiet :D

Many friends I work with (editing) are West Coast and that fosters the late working habit a bit for me as well :)

Wow, what a great read! Few things...You mentioned "dialing air valves on needle wheels" Care to elaborate? I have a ASM clone with a needlewheelthat I am just not happy with venturi. I feel it could be producing better bubbles. Right now I actually have a very small air pump running into the venturi which seems to help. Is this in line with your comment regarding string pressure air pump? Am i on the right track? Thank you in advance.

[QUOTE][B]... for nutrient control... and/or a brisk chaetomorpha refugium/vegetable filter.[/B][/QUOTE] Hey Antony, been awhile since you were out here and I have really enjoyed the Book of Coral Propagation. I have been using a Sea-Clone skimmer in my 120 w/ 30 G refugium, yes I know it is to small. The question is that with the chaetomorpha filling most of the refugium, should I expect much in the way of skimmate production? Two small fish, about 120Lb of LR and not a very heavy load of coral but a good sized cleanup crew.

I really don't see the Chaeto competing with a skimmer to the point of handicapping its performance much.

Seaclones have... er...a reputation for being... er, well... challenging shall we say, to get any consistent quality or quantity of skimmate out of.

If you put an Aqua C Remora on a tank with a Seaclone... you will be converted my friend ;)

That Aqua C model is categorically the best HOB skimmer IMO at any price and also happens to be a good value. FWIW

Anthony

Yeah, I do not like the Sea Clone but was using it until I figure what and where the new one will be and go. The MARS group has a well preforming DIY I was thinking on. But first I am building new prop tanks.

understood... indeed there are many fine DIY plans out there. Some work better than commercial models, but many such also require more daily tuning to get to that level FWIW.

The best skimmers I've ever used were 6' Nilsen style DIY jobs... but they are too laborious. I gladly use Aqua C, ASM or Euro-Reef instead now :D

Would you care to comment as to whether "wet" skimmate" removes more nutrients than "dry" skimmate?

I have noticed a dramatic increase in wet skimmate since I changed the recommended MAG 7 to a MAG 9 on my Aqua C (I'm very glad to see that is one brand you would use. :D ). In fact the wet skimmate production is so great that I have had to reduce the air to prevent overflow (copious amounts of almost clear skimmate). The gate valve is full open.

I have just got to the skimmer section in your book. Like others have said - so much info that it takes slow reading not to miss anything.

Vickie

It's been more than a few years since I read a comparative assays of skimmate quality re: wet vs. dry and between brands.

To generalize though... its not a good vs. bad contrast. Different skimmers and different skimmates (wet vs. dry again) extract different elements. So to some extent its a bit of an apples and oranges issue.

But I will say that is it better, as a rule, to draw darker, dense skimmate rather than wet.

For a skimmer that is pulling too much water, lower the active level (interface between water and foam) by opening the gate valve on the effluent/outgoing side slightly. The drop will make the foam climb higher and dryer. If this halts skimmate production instead of drying it out (darker skimmate) you may need to increase air and/or decrease bubble size as well. If that also does not work, then the problem may be design related (neck too wide for action relative to the air and water volume running through the unit).

[QUOTE]Back to those sump model skimmers... if you cannot seal a partition into your sump... and if you cannot fit a skimmer tank next to or above the sump... then stick the skimmer in a bucket in the sump so that it sticks up above the active running sump water level. Feed this bucket with (again) raw water from the display above, and simply let it overflow the sides of the bucket into the sump proper[/QUOTE]


Does it follow then, that the raw overflow which is fed into the dedicated skimmer area (or bucket) should have some sort of valve to control the flow into (and thus out of) the area?

So a slower flow/less turbulence into the skimmer area will help to optimize skimmer performance?

ScooterGuitar... do try adding a quality needle valve to the airpump. If nothing else, it gives you very fine control of the air being driven/aspirated. Are you using a strong airpump too? (one rated for pressure/deep tanks)

Salmon... I'm not sure what you mean by turbulence here. At any rate, no... you likely should not regulate the incoming water... waaaaayyyy too complicated. For optimal skimmer performance, you want to have only one variable (air or water). I favor fixing air, and keeping water adjustable on the outflow. If you then add a valve to the inflow, it becomes a juggling act and hard to produce consistent skimmate.

I cannot see why you'd need it either with water flowing directly into a skimmer or being collected in a skimmer well/dam (standing/static overflowing vessel).

Is there a design flaw/concern with your system that is producing (seriously here...) a crashing water fall like action?

Hi Anthony,

I think I failed to adequately explain my question.:o
Let me give it another try:

You've said that to help optimize skimmer performance, short of using a top mounted skimmer, that one might " get a small plastic or glass vessel (again... just large enough to squeak the skimmer into) and drill it to overflow into the sump".

If I'm directing the raw overflow into this vessel, and my turnover is 10-20x system volume, this is going to produce a hefty amount of turbulence in this vessel. Is that acceptable?

I understand that with said configuration the water level within the vessel will remain stable as it overflows at a preset level (dictated by the individual skimmer requirement?) into the sump, thus preventing variablility of pump head pressure.

Why would this be more advantageous than say a 4' long sump with raw overflow that enters at one end where it clears a baffle and travels to the other with the skimmer positioned in the center? If the sump water level is maintained constant at the ideal height for the skimmer via auto-top off, and excessive turbulence is controlled via a set of baffles where the raw water enters, would this not also be an optimal configuration?

Sorry, I'm not trying to be difficult...I'm just trying to understand why one configuration would be significantly advantageous than another.

Thanks for all the help! :)

Jeff

cheers, Jeff... all clear.

The problems are: 10-20X turnover (or higher) needs to be in the tank, but not necessarily through the overflow. For tanks requiring more flow particularly (as with shallow Acroporid sp, eg) this number is much higher and indeed causes quite a disturbance (even noise) if all run through one overflow box, skimmer box, etc. Hence the popularity of closed loop pumps (tapped into tank walls) and closed loop manifolds (fed by a pump other than the sump return). Thus, a moderate flow can make the display-sump loop (and any inline vessels like the skimmer chamber)... and a separate closed loop pump can handle the bulk of the tank's flow needs.

On your latter question re: the skimmer in a stable open sump... its not bad, but still not as good as a tight skimmer well/box. In a 4' long sump in this example... its even worse for the (large) sump size. Its the same problem as a HOB skimmer that is drawing water from 1, 2 or even 4" below the surface (however stable that might be): proteins get a chance to migrate to the surface and are separated/diluted away from the pump draw.

I think the problem that many folks have in understanding or visualizing this dynamic is the incorrect assumption that all water in the tank and subsequently drawn by the skimmer is "homogeneous" so to speak. When the fact of the matter is that proteins are migrating to the surface... surface of the display... and surface of the sump to your great disadvantage in larger sumps (versus tight little skimmer wells for concentration).

I'm not sure if I've succeeded in explaining that any better. Hmmm...

hoping so :)

Anthony-

I have a Truvu 300 arriving in a few days. My plan is for 1300gph through my sump, and 2 Sequence 750's (3000gph each) on closed loops. I'll have an ASM G4 in the sump, and planned on using a Maxijet 1200 to keep the proteins from accumulating on the surface in the sump. What are your thoughts on agitating the sump water surface in order to help get the proteins down to the skimmer intake?

On another note, the tank is 30" deep, I plan on running 2 400 halides and 2 250 halides, along with 4 48" T5 actinic. Do you think the 400's are overkill, even on a tank this deep. The plan is mainly for acropora species.

Thanks kindly,

Marc

Anthony-

Actually, that cleared it up very nicely. Makes perfect sense: Take as much water from the surface layer as possible and concentrate it into a small vessel so the skimmer can remove the proteins before they migrate to the top layer again.

So that 10-20x flow can be accomplished via closed loop or perhaps Tunze pumps/waveboxes as opposed to pushing ever increasing velocities of water through the sump.... that makes the plumbing a bit easier...:D

As always, my thanks.

Jeff

Jeff... you have summarized it most excellently my friend! Far better than my (typical) wordy, verbose effort :D

And Marc... spot on, mate. While we do not want to excessively disturb the display water's surface if the overflow will feed a skimmer downstream of it, you would definitely benefit by disturbing the sump (better homogenizing of the matter) if a skimmer is fed by sump water.

In my presentations/lectures and sharing advice... I often preach of "finesse" as making great long term difference in husbandry. Attention to details such as these go a long way. Beyond a quality skimmer, the exact placement, water stability (or not), "thin-ness" of overflow water (concentration of proteins), and so much more make a great imp[act at times.

A funny aside... have you ever noticed that your skimmer performance falters just before and during a storm? The drop in barometric pressure influences bubble size (production). It makes the bubbles larger ;)

re: lights, Marc

Its hard to say... pending tank size and species kept under it (and their needs).

To generalize though, if the tank is 200-300 galls, the total lighting is in the ballpark for a typical garden reef display.

As for the 400's being too much: I'd say not at all for tanks 30"+ and particularly if you are using 20k K lamps over deepwater species (LPS Euphylliids, Fungiids, and/or Corallimorphs for example)... or... 6500 K 400's over a dedicated shallow water sps tank.

no worries :)