Are we skimming too much?

[ScubaRaven]

I recently stumbled upon an article by Ken S. Feldman entitled "Elemental Anaylsis of Skimmate: What does a Protein Skimmer Actually Remove from aquarium Water.

In his article/analysis, he reports findings that only 1/3 of what is removed through skimmer is actually organic material, and that as much as 44% was actually CaCO3. Here's the summary of the article, along with link to the full article. Let's discus!

SUMMARY:

Conclusions
The chemical/elemental composition of skimmate generated by an H&S 200-1260 skimmer on a 175-gallon reef tank over the course of several days or a week had some surprises. Only a minor amount of the skimmate (solid + liquid) could be attributed to organic carbon (TOC); about 29%, and most of that material was not water soluble, i.e., was not dissolved organic carbon. The majority of the recovered skimmate solid, apart from the commons ions of seawater, was CaCO3, MgCO3, and SiO2 - inorganic compounds! The origin of these species is not known with certainity, but a good case can be made that the SiO2 stems from the shells of diatoms. The CaCO3 might be derived from other planktonic microbes bearing calcium carbonate shells, or might come from calcium reactor effluent. To the extent that the solid skimmate consists of microflora, then some proportion of the insoluble organic material removed by skimming would then simply be the organic components (the "guts") of these microflora. These microflora do concentrate P, N, and C nutrients from the water column, and so their removal via skimming does constitute a means of nutrient export.

LINK: http://www.advancedaquarist.com/2010/2/aafeature/

 

[Heliman]

Yes, an interesting article....but poses a few more questions than it answered !!

One pleasing aspect is another confirmation that effective skimming removes N, P and C from the water column, and that cant be bad. Although there are alternate methods available to us to remove these by-products (GAC, GFO, LC and C dosing), skimming seems a reasonable and safe mechanism to help in management of particularly Phosphates and Nitrates.

The questions posed by the lack of organic TOC in the skimate centre around the probabilities that the 39% mentioned is either all, or only part of the TOC in the water column.

If it is ALL of the TOC then the skimmer has done its job well ! If it is only part of the TOC in the water colomn, then to reduce skimming would leave some of this TOC unremoved.....and that cant be good !

Indeed, if 39% represents only part of the total TOC in the water, then there is a good case for MORE skimming, to get the other bit !

Of particular concern however is the finding that it does seem that the skimmer does not deal well with dissolved Organic compounds, which is where I for one, previously believed that the skimmer was essential to do just this.

In summary, the removal of P, N and C is a continuing justification for me to keep skimming 24/7

Thanks for the article...good read.

 

[swcc]

bacterial processes are still happening in the cup
What one tank collects may not be in any way a representation for what is in another tank's skimmate.

The articles sampling is way to small to determine anything of his findings...

 

[jdegrasse]

To answer your question -- no.

I don't think Dr. Feldman is implying that the skimmer is pulling out usable CaCO3 and so starving coral growth.

 

[ReeferBatman]

Good article... thanks for the read

 

[Ghosty]

Definitely good info to add to the debate. Lots of threads on the "is it possible to overskim" topic.

 

[Ron Reefman]

I find it interesting that there isn't a lot more research into this subject. It doesn't seem that difficult to collect some skimmate from some different sources and then test it for chemical make up. I'm no chemist, but it just doesn't seem that hard.

On the other hand, look at your skimmate, and at the volume of it you remove. Is that really stuff you want in your water? My eye's and my nose tell me I'd just as soon remove it.

 

[wayne in norway]

If skimmers were the devils own work as so often is claimed by people, how come so many peoples tanks improve when they get a skimmer upgrade?

 

[jdegrasse]

If skimmers were the devils own work as so often is claimed by people, how come so many peoples tanks improve when they get a skimmer upgrade?

:thumbsup:

 

[ReeferBatman]

I think a skimmer can be a good additional upgrade to a tank... but this article just solidifies my opinion that there are better methods to "foundation filtration" for your tank.

I personally think newbies would be better off spending their money on a nice canister filter and lots of life rock than skipping those and relying solely on a skimmer.

Thats not to say the skimmer won't help... just the amount of help for the cost is not as attractive IMO.

 

[hollister]

Skimming depends on your stock . Coral and pods and ect. do like a little waste. If you dont have to many fish then water changes should be enough.Water reading can help decide this.

 

[Garfield90]

If skimmers were the devils own work as so often is claimed by people, how come so many peoples tanks improve when they get a skimmer upgrade?

Because of the increase in oxygen levels. When you use a skimmer, the oxygen levels and ORP levels improve and pH always increases

 

[ksed]

Because of the increase in oxygen levels. When you use a skimmer, the oxygen levels and ORP levels improve and pH always increases

Well said. These are one of the main benefits of a skimmer.

 

[sabbath]

I have been running tanks since the 80's and I have not had good experience with depending on any one filtering device. I think many methods have pros and cons and using more then one creates better results IME.

I'm curentlly using;
-Filter socks changed twice a week
-Skimmer
-Zeolites Sized at 75% with low doses of start and bac
-ATS sized at 25%
-7% weekly W/C
-1/3 pound per gallon Live rock

 

[BeanAnimal]

Something things to consider

Lets take compounds A - Z

A water change reduces (by dilution) all compounds A - Z at the ratio of the dilution.
Skimming reduces a subset of A - Z be removal
An ATS reduces a subset of A-Z by removal (and may ADD another subset of A-Z)
Mechanical Filtration reduces a subset of A-Z by removal
Etc. etc.

The problem we have is that we are not dealing with fixed levels of A - Z where we can simply keep reducing them. We are adding some subset of A - Z and we can not ensure that the skimmer, or ATS or whatever is removing ALL of what we introduce. Add in a sand bed and/or other "nutrient sinks" and all bets are off. Each system is slightly (or vastly) different due to the number of variables.

No one filtration method is always a complete replacement for another, but in general we need more than one method because each removes different compounds in different ratios. In general there is no replacement for water changes and water changes are not a replacement for compound specific filtration.

Overskimming? Starving corals? No way... I dare any of you who think you have a "clean" overskimmed, mechanical filtered system to wrap the return pump intake in filter fabric, or discharge your overflow into a 5micron or 10micron filter sock. You will be shocked at the brown sludge that accumulates in a short period of time. I would venture to say that none of us are over filtering our tanks or starving anything, short of dragonets or other macro fauna specific feeders that are likely on the edge to begin with.

 

[E.intheC]

Good post Bean.

I'm going to add that you CAN have a skimmer that is too large. Not because it will remove too much, but because the neck is sized too large and there won't be enough proteins to build a stable head of foam. It might skim when enough organics build up, but I'd rather have a consistent amount of DOCs removed.

 

[swcc]

Because of the increase in oxygen levels. When you use a skimmer, the oxygen levels and ORP levels improve and pH always increases

Not quite correct...
skimmers do not increase oxygen levels...they do provide increased surface area with the atmosphere to help equalize co2 to said atmosphere. The increase in PH only might occur if the atmospheric co2 is lower than the tank co2. some folks that have very high co2 levels in their home have actually seen an increase in PH by turning off their skimmer(few and far between though). Generally, the increased surface area from the air pulled in by your skimmer does help, but not always.

A skimmer is the only export filtration device we have other than your siphon...This is where the real improvement comes from...it exports while all other filtration adsorbs other than UV which provides radiation.

 

[swcc]

Good post Bean.

I'm going to add that you CAN have a skimmer that is too large. Not because it will remove too much, but because the neck is sized too large and there won't be enough proteins to build a stable head of foam. It might skim when enough organics build up, but I'd rather have a consistent amount of DOCs removed.

That may not actually be correct either.
case in point is this study... http://www.advancedaquarist.com/2010/1/aafeature#section-3
in this study are 3 in sump needle wheel skimmer of very different size..the euro reef, the bubble king mini 160 and the vertex alpha 170....
as per comments section the author admits the amount of organics in the water were very low and at most he saw a ring formed in the neck of the skimmers over the two hour period... notice the total amount of organics removed over the two hour period... the euro reef(smallest neck and air) pulled 20%+/-6...the bubble king pulled 37%+/-6 and the alpha 170 pulled 24%+/-12. The euroreef also pulled the fastest for the first hour between the three... so commonly it is believed that larger skimmers pull faster but not as deep into the organics...well... right in this study the opposite happens and the smaller skimmer pulled faster yet not nearly as deep into the organics...the alpha 170 pulled on average 20% more organics and the mini 160 pulled a whopping 85% more organics over the smaller euro reef. While that was not the intention of the study, to me this is a point one should not overlook and may in some way disprove that a smaller skimmer is not necessarily better than a oversized skimmer when it comes to reducing organics in lighter bioloads.

 

[E.intheC]

Those are three different skimmer models. On one tank. The sample isn't large enough to draw conclusions surrounding my previous comment.

I saw it first hand on my tank.. The larger skimmer pulled more for the first few days, then almost nothing. While the properly sized skimmer pulled less right off the bat, but skimmed more consistently.

Even if they both pull the same amount of gunk out of the water, I'd rather have the same amount pulled consistently rather than a large amount pulled, then nothing, then a large amount... Etc.

 

[swcc]

Those are three different skimmer models. On one tank. The sample isn't large enough to draw conclusions surrounding my previous comment.

I saw it first hand on my tank.. The larger skimmer pulled more for the first few days, then almost nothing. While the properly sized skimmer pulled less right off the bat, but skimmed more consistently.

Even if they both pull the same amount of gunk out of the water, I'd rather have the same amount pulled consistently rather than a large amount pulled, then nothing, then a large amount... Etc.

what were your larger vs properly sized skimmers? When you ran the larger skimmer did you also run a larger return pump feeding it more display water?

Point I was making is that the 2 much larger skimmers tested did in fact reduce organic load lower than the smaller skimmer time and time again.(which disproves the blanket belief that larger skimmers require more organics and will not reduce as much when the bioload is small). If that were the case then both the vertex and bubble king should not have been able to compete with much less perform better than the euro reef on the very low bioload. True a better comparison would be comparing the same skimmer of different sizes on the same organic load... maybe someday someone will do a study of just that.