"Natural Filtration"

[HecticDialectics]

You would actually be surprised what's out there and for what.

 

That would be awesome if ya could find somethin. Hell of a job!

[Urchinhead]

Coming back around at this and going back to read what I could (not going to pay $34 for the article HD came up with) it looks like there is a fundamental flaw both in the arguments being presented here regarding removal of Ca/CaCO3/etc via skimming and in the research done to date.

 

Specifically there doesn't seem to be any analysis of what the effect of skimming has on the levels of various elements in the overall tank water. Wombat mentions that it would be negligible relative to overall levels but there doesn't seem to be anything to support this supposition. So far all I can see is that there are "beneficial" elements (Ca/CaCO3/I/etc) in skimmate but nothing showing what the amount removed has impact wise on the levels in the water column.

 

The article Wombat links to does state that its possible that the Ca et al. may be particulates from the Ca Reactor and/or from the skeletons of various inverts (copapods et al) caught up in the skimmate but doesn't confirm this.

 

Also there seems to be some cases of correlation doesn't show causation error in play. Specifically Ca et al. are found in skimmate at appreciable levels ergo skimmers remove said elements and are thus bad.

 

Wouldn't simply setting up two identical systems without anything other than water normalized to a set level of each element and at the same salinity/pH/temp, one with a skimmer and one without, then monitoring the levels of "beneficial" elements in each tank over N amount of time with appropriate controls for environmental factors such as normal evaporation, replacement with RODI water etc. answer the overall question of what the impact a skimmer has on the levels?

 

Pretty straight forward and inexpensive experiment at the end of the day, no?

 

The one question I am too lazy to work out for myself (looking at Wombat) would be what substance to use to stimulate the skimmer that would not skew the test due to introduction of additional elements being tested for...?

 

That would be awesome if ya could find somethin. Hell of a job!

 

Now that construction on my house is done and things at work are settling down into normal noise levels the two things that are interesting to me at the moment are this one and what the actual growth rates for corals are under LED vs. traditional lighting.

 

With that said I may, if I can get off my lazy rear end, decide to work something up where I could get some funding for this. I can write a pretty mean grant proposal when I have to. My only worry is that the amount requested will be so insignificant compared to what is considered the "norm" that it gets tossed for being too small... Sadly this has happened in the past to me and others I work with.

[lakshwadeep]

You could use bovine serum albumin (BSA) or other proteinaceous compound, but I think it's also be worthwhile to just measure a normal tank's parameters with and without skimming.

[wombat]

Specifically there doesn't seem to be any analysis of what the effect of skimming has on the levels of various elements in the overall tank water. Wombat mentions that it would be negligible relative to overall levels but there doesn't seem to be anything to support this supposition. So far all I can see is that there are "beneficial" elements (Ca/CaCO3/I/etc) in skimmate but nothing showing what the amount removed has impact wise on the levels in the water column.

 

That is certainly interesting, but outside the scope of the article. You can confirm for yourself that the amount is negligible with a bit of arithmetic and chemistry. Ken found the skimmer removed a total of 545mg of Ca from a 175g (or 665L) tank. This is 0.8 mg/L, over a few days. The concentration of calcium in seawater is in the neighborhood of 400mg/L, give or take 20mg/L.

 

So even if you assumed* that all of the calcium that the skimmer removed was in solution, it still would have only removed around 0.2% of it. This is negligible IMO.

 

*Our best guess is that most of the calcium in the skimmate is NOT soluble, but in the form of CaCO3 as coccolithophores or as part of fish feces. This is something we can't confirm without a fancy tool like a scanning electron microscope, which is exactly what I plan to do soon.

 

The article Wombat links to does state that its possible that the Ca et al. may be particulates from the Ca Reactor and/or from the skeletons of various inverts (copapods et al) caught up in the skimmate but doesn't confirm this.

 

Right, it's not easy to confirm it. See above.

 

Also there seems to be some cases of correlation doesn't show causation error in play. Specifically Ca et al. are found in skimmate at appreciable levels ergo skimmers remove said elements and are thus bad.

 

Who is saying that? I'm certainly not saying that. The author of the article is not saying that.

 

Wouldn't simply setting up two identical systems without anything other than water normalized to a set level of each element and at the same salinity/pH/temp, one with a skimmer and one without, then monitoring the levels of "beneficial" elements in each tank over N amount of time with appropriate controls for environmental factors such as normal evaporation, replacement with RODI water etc. answer the overall question of what the impact a skimmer has on the levels?

 

Pretty straight forward and inexpensive experiment at the end of the day, no?

 

Unfortunately, it is not that straightforward or simple. You can set up two "identical" systems, treat them exactly the same in every way imaginable, and then test them for calcium, alkalinity, pH, any element you like, etc. with the most accurate analysis available and you will find they are very different from day to day in unpredictable ways. As soon as you throw some live rock into the tank, you can forget about them being identical anymore. There are simply too many variables at play once you start throwing living organisms into the mix.

 

So, how do you tease out how what effect the skimmer is having on that chaos, when we've already shown that, even under the very best of circumstances, the skimmer would only have an effect of 0.2%?

[Urchinhead]

That is certainly interesting, but outside the scope of the article. You can confirm for yourself that the amount is negligible with a bit of arithmetic and chemistry. Ken found the skimmer removed a total of 545mg of Ca from a 175g (or 665L) tank. This is 0.8 mg/L, over a few days. The concentration of calcium in seawater is in the neighborhood of 400mg/L, give or take 20mg/L.

 

So even if you assumed* that all of the calcium that the skimmer removed was in solution, it still would have only removed around 0.2% of it. This is negligible IMO.

 

*Our best guess is that most of the calcium in the skimmate is NOT soluble, but in the form of CaCO3 as coccolithophores or as part of fish feces. This is something we can't confirm without a fancy tool like a scanning electron microscope, which is exactly what I plan to do soon.

 

Didn't catch that when I read it but you're right. Too blinded by my own thoughts.

 

Now about that scanning scope... Where are you located again...? And where DO you get access to those great toys!?!

 

 

Who is saying that? I'm certainly not saying that. The author of the article is not saying that.

 

The folks here who are saying that skimming is bad bad bad because it removes elements from the wc.

 

Unfortunately, it is not that straightforward or simple. You can set up two "identical" systems, treat them exactly the same in every way imaginable, and then test them for calcium, alkalinity, pH, any element you like, etc. with the most accurate analysis available and you will find they are very different from day to day in unpredictable ways. As soon as you throw some live rock into the tank, you can forget about them being identical anymore. There are simply too many variables at play once you start throwing living organisms into the mix.

 

So, how do you tease out how what effect the skimmer is having on that chaos, when we've already shown that, even under the very best of circumstances, the skimmer would only have an effect of 0.2%?

 

Yes I agree on variables. There in lies the rub. The idea was that the tanks would have nothing in them besides water and something to simulate DOC in the skimmer tank to stimulate skimmer function.

 

Never mind. It doesn't need "proving" since we can extrapolate based on findings on the actual removal. Sigh. I am really in need of something interesting to do that I may be able to write a decent paper on since I can't do that with what I do professionally thanks to work restrictions I guess I am grasping at whatever floats by in one of my hobbies. Rather sad when you think about it.

[wombat]

I am really in need of something interesting to do that I may be able to write a decent paper on since I can't do that with what I do professionally thanks to work restrictions I guess I am grasping at whatever floats by in one of my hobbies. Rather sad when you think about it.

 

Not sad at all! You are interested, and looking, and willing to do it! Now you just need a subject. I like writing about stuff that I think I'm good at. So, try to figure out what you're good at! It doesn't necessarily need to be scientifical-like, either. You might be surprised how eager some of the online and print magazines are to publish content from new authors.

 

Oh, by the way I work for the California Academy of Sciences in SF. Fancy tools and loads of great opportunities to answer interesting questions.

[Urchinhead]

Cheers mate. One of the things I really enjoy about this hobby is its strong foundation in the sciences. Sometimes to the detriment of my aesthetic appreciation of it.

 

Ah! This explains it! Very nice! I envy you! When I went to work where I work now I had the same opportunities for solving interesting problems it sound like you do. Unfortunately my cohort did our jobs a bit too well to fast and now the opportunities for interesting work are now rather few and far between and I have been here too long now to go back into private industry especially in this economy...