What does "over skimming" actually mean?

[tmz]

<a href=showthread.php?s=&postid=11059808#post11059808 target=_blank>Originally posted</a> by MCsaxmaster
It is fairly easy and reasonably common to have NSW levels of dissolved inorganic N and P. In captivity DON and DOP are often somewhat elevated compared to nature, but a bigger skimmer may not change this. There is also much, much less plankton and POM in most tanks as compared to nature. Skimmers can exacerbate this problem.

cj

I think you can easily overskim and starve your filter feeders as well as some corals. The upper reef is low in nutrient but not nutrient poor due to the massive amounts of water passing over it constantly replenishing life giving elements.It is also worth noting that deeper water corals live in significantly higher nutrient water than those at the top. Some that rely to some degree on absorbtion such as xenia ,nemenzophylia and pssibly blastomossa seem to need higher levels of nutrient. While others (sps) require lower levels. But they all require nutrients.

 

[jerryz]

So is it clear that skimmers remove plankton? Or is that just assumed? Or is that a byproduct of the removal of water? They are pretty large to be captured by bubbles.

 

[tmz]

Ithinkj they removce some. Phyto for sure and certainly dissoved organics and bacteria. Many filter feeders rely on the smaller foods.

 

[kysard1]

Somewhere I read that skimmate is mostly composed of plankton.


I once had a skimmer that was way too big for the tank. It could maintain a head of foam. I got very little skimmate. When I replaced it with a smaller skimmer I actually got much more skimmate.

 

[murraycamp]

Eric Borneman is supposed to be completing his skimmate study at some point, so that will be interesting.

FWIW, I would rather have the problem of having to increase feeding levels to ensure consistent skimmate production than reduce feeding levels because of nutrient export limitations in the system.

 

[murraycamp]

Forgot to include the link to Borneman's study info:

http://forum.marinedepot.com/Topic52254-9-1.aspx

 

[tmz]

<a href=showthread.php?s=&postid=11065254#post11065254 target=_blank>Originally posted</a> by murraycamp
Eric Borneman is supposed to be completing his skimmate study at some point, so that will be interesting.

FWIW, I would rather have the problem of having to increase feeding levels to ensure consistent skimmate production than reduce feeding levels because of nutrient export limitations in the system.

I agree for most aquaria,especially sps dominated tanks but not if you are trying to raise certain things like xenia. This is one of the reasons mixed tanks are difficult to keep,since the balance is hard to find.

 

[stony_corals]

I have xenia that grows like a weed in very nutrient poor systems 0ppm NO3 on LaMotte, and 0ppm PO4 on Merck.

I think the advantage of having good exports means is that you can put a lot more food into the tank. I'm trying to see how far I can push this... right now. On around 150g system, I'm feeding 1/2 teaspoon of food (Cyclopeese, Formula 1, ORA GLow, Zooplankton, or mysis) 4-5 times daily. The water column remains nutrient poor though due to export.... What I think would be ideal is to feed hourly, but I'm not there yet, to simulate the surges of food sources, but to maintain a nutrient poor environment.

 

[tmz]

I have a 400g system with many corals and about 30 fish and refugia. I feed well 2x per day. When I went to a larger skimmer my xenia waned. Some survived and are still dong ok but not spreading like they used to. Your approach of more frequent feeding and high export is intersting and certainly seems to get closer to natural cycles. Plese psodt your findings.

 

[stony_corals]

tmz, I know people that have sps dominate systems that experience this as well. My systems are 95% sps as well, I haven't. Could there be something else happening? Probably, may be its the feeding. I wish I had two identical systems to see the effects of feeding and growth/colorization, etc... I don't

Back to the topic at hand... when I think overskimming, I think, my skimmer is so big, relative to the system, I don't get much foam. I HAVE experienced this.... Try putting a large Beckett on a 120-130g system, all sps and clams, not fish... No foam (until I started feeding cyclopeese and Pappone).

I think what Chris talked about is different, it's from the perspective of the animals. They aren't getting the N and P, and their decline and demise happens, albeit slowly. We mostly see this with sponges, sea squirts, feather dusters etc...

I guess in the end it's semantics though...

 

[m2434]

Different corals have the competitive advantage under different nutrient and organic loads. If you skimm more the advantage shifts to species with lower requirements. Therefore an empirical definition for "over-skimming", for a particular coral, is easy... it is the point that the coral starts to starve. Over-skimming as a general use term however is just a heuristic concept with no real meaning, there are many levels of "over-skimming". I think the question then becomes can you skimm to the point nothing can live, this would be the final level of over-skimming, but then would it would still be theoretically possible to skimm more? Could you skim to the point you are left with pure water? The whole concept is somewhat foolish. It's too general. For the term to be of any use, there needs to be a relationship to biology.

 

[tmz]

I get the semantics but it is usefull to determine how much nutrient you wish to keep in the water for the particular population of corals. . If you can determine an optimal nutrient level for a particular captive reef (a level at which you are able to keep the corals you choose to keep in a vibrant and aestheticaly pleasing state) then the notion of overskimming or underskimming for that matter is useful since skimming may be your main nutrient exporter.

 

[m2434]

<a href=showthread.php?s=&postid=11093710#post11093710 target=_blank>Originally posted</a> by tmz
I get the semantics but it is usefull to determine how much nutrient you wish to keep in the water for the particular population of corals. . If you can determine an optimal nutrient level for a particular captive reef (a level at which you are able to keep the corals you choose to keep in a vibrant and aestheticaly pleasing state) then the notion of overskimming or underskimming for that matter is useful since skimming may be your main nutrient exporter.

It could be useful if you could quantify it. If you say you have high salinity, what does that mean 1.026, 1.027, 1.035. Without a way to measure it, it is nothing more than a buzz-word.

 

[tmz]

The amount of nutrient can to some degree be quantified and measured with testing for certain elements. There are also clues form the ocean where measure
ments of elements such as nitrogen and phosphorus have been taken at different depths on the reef where different corals reside. Many aquarists think in terms of removing as much nitrate and phosphate and disopved organics as you possibly can via reactors and skimmers (which also remove some helpful plankton). The notion of overskimming or overcleansing or whatever phrase is used is a worthy caveat even if a vague one.

 

[m2434]

Well, high salinity I guess is a worthy caveat, just a very vague one of very limited use. I can't count the number of times, on these forums, I've seen someone say may salinity is too high and after being asked what it is, disclose that it is 1.025... As far as skimming goes, If you measure nitrate in the tank, how do you know that it isn't being reduced to nitrogen gas by bacteria. Or phosphate isn't being taken up by algae. There is a lot of "cleaning" going on, on it's own. To attribute it to skimming, you would need to test what is being collected as skimmate. Then it would be possible to define overskimming, i.e. x amount of product y over time z per gallon of system water.... This would be useful. It would be more enthusiastic about the use of the term, if someone came up with a good metric. It's certainly possible, there's really no reason why scientists or eve hobbyists couldn't come up with one....

 

[murraycamp]

There is a lot of "cleaning" going on, on it's own. To attribute it to skimming, you would need to test what is being collected as skimmate. Then it would be possible to define overskimming

Great point. I hope Borneman's study helps to (at least somewhat) clarify this as well. I also like the idea of describing the concept as "over-cleaning." Generally, this discussion further supports my belief that reef keeping still has a significant "art" component, supported by the science.

 

[stony_corals]

There was a study done by Japanese scientists (from RA3) that showed that Mg was found in skimmate. I think it takes a lot out, stuff you wouldn't think.... remember that skimmate is 95% water too (or something like that)....

Unless your corals, sps specifically, are very pastel, and everything dies off from your live rock, I'd say your probably ok. However, if you use a huge a@#$ skimmer on a small tank and get no skimmate, you might be over skimming (sound like Jeff Foxworthy there)....

 

[hahnmeister]

I was reading in the Ultimate Reef forum (UK) that they consider 'overskimming' to be the point where you have stripped your water from anything that corals might consume... bad or good... and your polyp extension goes down the toilet as a consequence.

 

[murraycamp]

Unless your corals, sps specifically, are very pastel, and everything dies off from your live rock, I'd say your probably ok. However, if you use a huge a@#$ skimmer on a small tank and get no skimmate, you might be over skimming (sound like Jeff Foxworthy there)....

That's sounds reasonable.

Foxworthy. Hmmmmmmm. Interesting start of a new thread:

You might be a novice reefkeeper if . . .

 

[hahnmeister]

So what if my SPS are pastel looking? Lol.