Is it possible to over skim?

Is it possible to over skim?

  • Yes

    Votes: 7 18.4%
  • No

    Votes: 26 68.4%
  • Depends

    Votes: 5 13.2%

  • Total voters
    38
  • Poll closed .

reefology1

New member
From a chemistry point of view, assuming we do at least 10% monthly water changes, can we pull out too much of something eventually throwing our system out of balance?
 

tmz

ReefKeeping Mag staff
Premium Member
I'm not sure waht "overskimming " means exactly.

Water cahnges replenis h major, minor and trace elements and pull excesses back toward starting ratios.

Generally, skimming's effect on corals depends on the corals kept along with other variables like :GAC use and feeding for example.IME.

Some corals with higher hetrotrophic needs ; xenia , capnella(kenya tree),ricordea, and nemenzohoplyllia( fox coral) for example do better in lightly skimmed water . Probably because there is more DOC, in a variety of organic campounds in the water, which they take up .

Others like many sps, zoanthus , and some favia do better in more heavily skimmed water.

Many like calaustrea, euhpylllia, gorgonia, sacrophyton, sinularia and nepthea do reasonably well in either case.

It should be noted skimming though it does remove some particulate matter and amphipathic organic compounds is also a very good source of aeration promoting beneficial gas exchange.
 
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Coralfreak09

New member
I'm not sure waht "overskimming " means exactly.

Water cahnges replenis h major, minor and trace elements and pull excesses back toward starting ratios.

Generally, skimming's effect on corals depends on the corals kept along with other variables like :GAC use and feeding for example.IME.

Some corals with higher hetrotrophic needs ; xenia , capnella(kenya tree),ricordea, and nemenzohoplyllia( fox coral) for example do better in lightly skimmed water . Probably because there is more DOC, in a variety of organic campounds in the water, which they take up .

Others like many sps, zoanthus , and some favia do better in more heavily skimmed water.

Many like calaustrea, euhpylllia, gorgonia, sacrophyton, sinularia and nepthea do reasonably well in either case.

It should be noted skimming though it does remove some particulate matter and amphipathic organic compounds is also a very good source of aeration promoting beneficial gas exchange.

This guy is spot on, you cant exactly have a direct yes or no, answer. Its best to play around with your skimmer and watch to see how your tank reacts until you find that sweet spot. I just bought a new skimmer and am doing the same thing. Aeration is great, but micro bubbles in main display are no good, again find the balance.
 

bertoni

Premium Member
In theory, a skimmer might be able to remove enough nutrients from the water column that some corals might starve, but that seems hard to accomplish in reality. Is your system having some sort of problem, or is this more a question about getting ready for a purchase?
 

tkeracer619

Premium Member
Feed more often and better foods, go for ulns through carbon dosing, decrease bubble size, better surface skimming, and add more livestock.
 

tmz

ReefKeeping Mag staff
Premium Member
Say you do have an oversize skimmer for the system size you have, is there anything you can do to improve its performance.

If you mean produce darker drier skimmate ,then adjusting the water column in the skimmer to a lower level will usually produce a higher and drier column of foam. Not sure that's and improvement ;though, it will save on the amount of water exported.
Turning the skimmer on and off on a timer is another option but then the aeration will also be reduced.
Sometimes, there just aren't enough amphipathic organics in the water for much to be trapped in the air/water interface along the bubbles' surfaces to create concentrated skimmate. For example, I run two large needlewheel skimmers on my system with a rel tively high water column in each. They produce a lot of dark odiferous skimmate from the heavily fed ,high bioload system which is also dosed with moderate amounts of vodka and vinegar. In a lightly fed system the skimmate would probably look closer to clear water.
 
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snorvich

Team RC member
Team RC
If you mean produce darker drier skimmate ,then adjusting the water column in the skimmer to a lower level will usually produce a higher and drier column of foam. Not sure that's and improvement ;though. it will save on the amount of water exported. Turning it on and off on a timer is another option but then the aeration will also be reduced.
Sometimes, there just aren't enough amphipathic organics in the water for much to be trapped in the air/water interface along the bubbles' surfaces to create concentrated skimmate.

What he said. Dark and thick is a matter of choice but it does not necessarily mean that life is better. I do not suggest skimming via a timer because of oxygenation.
 

reefology1

New member
In theory, a skimmer might be able to remove enough nutrients from the water column that some corals might starve, but that seems hard to accomplish in reality. Is your system having some sort of problem, or is this more a question about getting ready for a purchase?

no purchase or problem to speak of. the reason i ask is I've mostly relied on "over skimming" (over the last 20 yrs) as the only means of nutrient export and have always had good water quality. like most, i base this on hobby grade test kits for Alk, Ca, Mg, N03 and P04.

Though I've had great systems and success (relative term) with sps, I never seem to get the vibrant colors and growth rates others seem to have. I've always fed sparingly in the past but have started to feed alot more and dose vinegar conservatively in my new sps setup (6 mths). have also been contemplating dosing potassium but not convinced i need to.

My concerns are perhaps i'm inadvertently pulling out essential minerals or minor element (i don't or can't test for) via skimming and wondering what others (on this great forum) thought/think about "over skimming" and how it may or may not effect water quality?
 

tmz

ReefKeeping Mag staff
Premium Member
Skimming removes some organic material that may include some major , minor and trace elements.
GAC probably removes more .

I use both and do not dose any minor, major or trace elements other than kalk for alk and calcium. Corals including sps are vibrant. Food and water changes (1% daily) seem to take care of everything else including: K , idodine, iron which I test infrequently .
Organic carbon dosing( vodka and vinegar) eanble heavy feeding with low PO4 and NO3. I do not aim for zeros in NO3 or PO4. For me PO4 ranging from .02ppm to .04ppm and NO3 0.2ppm to 1pmm have been adequate to meet the corals needs without much nuisance alge. Some like higher levels.
 

bertoni

Premium Member
I agree that skimming can remove trace elements that are bound to organics. Given the feeding level for most of our tanks, I don't think that removing trace elements like that is bad.
 

biecacka

New member
I skim a light greenish tea colored skim, I'm lowering my water level a bit to get a darker color. For personal preference only tho. As it sites now, my skim cup is covered in a dark nasty sludge so I'm pulling it out which is all I'm worried about. I don't think one can over skim, I once read that the best skimmers can only pull out about 30% of the DOC anyway.

Corey
 

tmz

ReefKeeping Mag staff
Premium Member
I've read it's more like 18%with GAC in the 30% range The question for me is which organics are in the the skimmer is pulling out , whether they are all harmful, whether some are useful and to what extent they are replaced via feeding and or photosynhthetic activity and stuff like coral slime,and other exudates.
 

reefology1

New member
I've read it's more like 18%with GAC in the 30% range The question for me is which organics are in the the skimmer is pulling out , whether they are all harmful, whether some are useful and to what extent they are replaced via feeding and or photosynhthetic activity and stuff like coral slime,and other exudates.

precisely? thank you Tom.

wondering if anyone can point us to this info? if it exists...
 

tmz

ReefKeeping Mag staff
Premium Member
There are a number of papers on foam fractionation in the sea if you want to search for them.

There isn't any information on the mix in DOC in reef tanks as far as I know.

There is an excellent article by Randy Holmes Farley on how skimmers work and another on organics. Both are cited below. They will get you started in trying to gain insights from your own observations :

http://reefkeeping.com/issues/2005-12/rhf/index.php


http://reefkeeping.com/issues/2004-10/rhf/index.htm

Organics are very complicated ;most are still unidentified ;there may be millions of compounds . We do know that proteins are amphipathic( positive charge on one end and negative on another) and that they are thus attracted to the air/water interface between the bubbles; hence, the term protein skimmer. We also know some organics are refractory( resitive to further degradation ) and some of those are removable by skimming .We also know skimming removes compounds that discolor the water ,yellowng compunds, aka "gelbstuff",as does GAC. Some bacteria are pulled out too. DOC level really doesn't tell us enough about the mix of organics in the total DOC and which types are removed vs remain . GAC may pull out many of the same organics as skimming but seems from what I've read to have more affinity for hydrophobic compounds ,those repelled by water , which is not surprising given the fact that GAC works on a weaker force( Van der Walls force) as opposed to charge based attractions and repulsions.
 
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