Oceamo Skimmate Analysis Results Discussion

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Randy Holmes-Farley

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I do find it very interesting that the nutrient levels of this skimmate are so low. If I’m reading right? I’m sure many would consider those levels as being perfectly fine for tank water and some might even be envious and that is where the real questions come in my mind.

There's more than 20 ppm phosphate equivalent in the skimmate. I don't know what one would hope or expect it to be, since that value is very complicated by the many forms being counted, including whole bacteria.
 
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Randy Holmes-Farley

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goal here? To understand what elements may be stripped by skimming?

IMO, yes. While the results may not have immediate consequences for any particular reefer, I think it is useful and interesting to understand where some of the chemicals in the tank end up. Same as analyzing harvested algae or foods for elements. That sort of info may be useful for folks considering whether to skim or not, and to what extent, and if making changes to skimmers, what sorts of changes in the tank chemistry profile might have to be investigated.
 
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Randy Holmes-Farley

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Quickie analysis that is very interesting (IMO). Looking at skimmate vs tank, we can see which trace elements are most enriched in the skimmate. Hopefully i transcribed all numbers correctly...

Some of these results are expected (e.g., poor enrichment for lithium which neither binds organics nor gets taken up much by organisms) and some maybe not so much (poor enrichment for molybdenum and vanadium, for example).

1737724932417.png
 
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IMO, yes. While the results may not have immediate consequences for any particular reefer, I think it is useful and interesting to understand where some of the chemicals in the tank end up. Same as analyzing harvested algae or foods for elements. That sort of info may be useful for folks considering whether to skim or not, and to what extent, and if making changes to skimmers, what sorts of changes in the tank chemistry profile might have to be investigated.
so you've collected the skimmate during 400 days to have 0,658 l skimmate, so meaning it's extreme dry skimmate, becomes a paste ? Because even in my tank when i do dry skimmate, can get easily during 2-4 weeks the same paste amount 600ml or gram, my tank has only 550litres
 

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I think protein is the least that is skimmed from seawater/saltwater with air bubbles. In seawater bubbling seems to collect mainly exopolymers (slime):

There are a lot of other and newer articles on bubbling and TEP.
In the other thread when I originally brought up what might be exported in skimmate this is kind of where my thoughts were at. I have a mixed reef that I have been pouring lots of food into trying to keep a diverse group of animals including nps corals and filter feeders. I expected to have serious algae issues but don't. In fact after rebooting in mid November 2024 I fought off the uglies including dinos, cyano, hair algae, bryopsis (introduced on a coral) and diatoms all while pouring in foods. My observation is that my skimmate has never been thicker and darker and my water column is usually cleared within hours of feeding. I am curious if perhaps the addition of phyto was binding up other things and dragging them out thru skimming. By all rights my tank should be a cesspool but it is not, I have white sand and CLEAN rocks. I have been very surprised by these results. My concern was if the skimmer was that efficient was it also taking out things like (and I may be way off base here ) things like lipids, fatty acids, carbohydrates etc. Again, not a scientist here.
 

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Quickie analysis that is very interesting (IMO). Looking at skimmate vs tank, we can see which trace elements are most enriched in the skimmate. Hopefully i transcribed all numbers correctly...

Some of these results are expected (e.g., poor enrichment for lithium which neither binds organics nor gets taken up much by organisms) and some maybe not so much (poor enrichment for molybdenum and vanadium, for example).

1737724932417.png
Hmmm… So what’s up with Tin?
Can we hypothetically say that most comes from food and stays in the food chain?
Tank water zero….
 
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Randy Holmes-Farley

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so you've collected the skimmate during 400 days to have 0,658 l skimmate, so meaning it's extreme dry skimmate, becomes a paste ? Because even in my tank when i do dry skimmate, can get easily during 2-4 weeks the same paste amount 600ml or gram, my tank has only 550litres

I'm not understanding your point.
 

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some maybe not so much (poor enrichment for molybdenum and vanadium, for example)
Why not so much?

It could mean, and this is not unlikely, that mainly cations are bound to organics. Molybdate and vanadate are anions. There is some logic behind less anions being bound by organics. The charges on the surfaces of the organic molecules are mainly negative.

Rather the strong enrichment of selenite/selenate is a surprise. Some specific enrichment by organisms? Organic selenium? https://www.sciencedirect.com/science/article/abs/pii/0304420383900993
 
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so you've collected the skimmate during 400 days to have 0,658 l skimmate, so meaning it's extreme dry skimmate, becomes a paste ? Because even in my tank when i do dry skimmate, can get easily during 2-4 weeks the same paste amount 600ml or gram, my tank has only 550litres
it was collected in 4 days, not in 400 ;-)
 
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Randy Holmes-Farley

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Hmmm… So what’s up with Tin?
Can we hypothetically say that most comes from food and stays in the food chain?
Tank water zero….

Tin is an especially interesting result. The fact of the matter is that in many cases, I believe tin comes from release from plastics, and that form of tin is organically bound already in the plastic, and would be readily skimmable as made. The tin might also switch to other organics, and bare tin ions may bind natural organics, but here are what some tin additives for plastic (including FDA and NSF approved applications) look like, which I'd expect to be heavily skimmed.

1737727106569.png


1737727188328.png
 
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Why not so much?

It could mean, and this is not unlikely, that mainly cations are bound to organics. Molybdate and vanadate are anions. There is some logic behind less anions being bound by organics. The charges on the surfaces of the organic molecules are mainly negative.

Rather the strong enrichment of selenite/selenate is a surprise. Some specific enrichment by organisms? Organic selenium? https://www.sciencedirect.com/science/article/abs/pii/0304420383900993

Yes, that's a very good point, and may provide a way to determine, in a very rough sense, how much of the observed effects comes from elements in organisms (would contain natural vanadium and molybdenum), and how much from skimmed dissolved or particulate organics (which may not be enriched at all in those elements).
 
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Our protocol involves 1) cleaning the cup with RODI, 2) collecting skimmate for a specific timeframe (several days, number of days should be noted) 3) homogenizing the skimmer cup content with a supplied plastic spoon as good as possible 4) drawing the sample using a syringe.

That procedure seems reasonable to me. :)

After you do the acid dissolution, is there much solid residue? perhaps things like silica from diatoms?

Do you think any organic remains?
 

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There's more than 20 ppm phosphate equivalent in the skimmate. I don't know what one would hope or expect it to be, since that value is very complicated by the many forms being counted, including whole bacteria.
So, if you remove 100 ml skimmate from a 100 l tank, you are exporting 20 /1000 = 0.02 ppm phosphate. In reality should be less, as you are unlikely to get 100 ml skimmate from 100 l tank.

If you feed 1 g of dry fish food, very roughly, it contains around 0.01 g of phosphorus (based on Redfield ratio), or 0.03 g PO4, or 0.3 ppm in a 100 l tank. This would mean that we are exporting an order of magnitude less phosphorus, than we are adding, and it should result in its quick accumulation.
 
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So, if you remove 100 ml skimmate from a 100 l tank, you are exporting 20 /1000 = 0.02 ppm phosphate. In reality should be less, as you are unlikely to get 100 ml skimmate from 100 l tank.

That is what the math from this one tank suggests. I have no idea what this tank's husbandry techniques are. There are many sinks for phosphate that are possible, including corals, algae, macroalgae, precipitated onto and into calcium carbonate and other solids, bound using GFO or lanthanum or iron or aluminum oxide. Might be partly removed by water changes, or via the binding of organics with GAC, purigen, a polyfilter,

Phosphate itself is not skimmable, and I've never claimed skimming was a great way to reduce phosphate.
 

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That is what the math from this one tank suggests. I have no idea what this tank's husbandry techniques are. There are many sinks for phosphate that are possible, including corals, algae, macroalgae, precipitated onto and into calcium carbonate and other solids, bound using GFO or lanthanum or iron or aluminum oxide. Might be partly removed by water changes, or via the binding of organics with GAC, purigen, a polyfilter,

Phosphate itself is not skimmable, and I've never claimed skimming was a great way to reduce phosphate.
Yes, phosphate itself isn't skimmable (unless it becomes lanthanum or cerium phosphate, or even iron phosphate), but as Hans-Werner pointed out, the skimmer mostly removes slime. If we dose carbon, bacteria will eat it and be skimmed as slime - I would expect a higher ratio of phosphorus in the skimmate if that was the case. But, as you pointed out, we do not know about this tank's husbandry.
As for corals: yes, they do eat a lot. But if they eat all this excess phosphorus, their daily volume increase would very roughly match the wet amount of food that was added.
 

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That procedure seems reasonable to me. :)

After you do the acid dissolution, is there much solid residue? perhaps things like silica from diatoms?

Do you think any organic remains?
But what actually gets injected into the ICP-MS?

0.22 μ filtered solution of slurry? Acidification of skimmate slurry to dissolve preciptates followed by 0.22 μ filtration? Not sure what’s being measured and therefore not sure if we are seeing the whole picture of what a skimmer is removing.
 

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But if they eat all this excess phosphorus, their daily volume increase would very roughly match the wet amount of food that was added.
This doesn’t seem right to me. I don’t think you can correlate volume of food consumed to volume of growth
 
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Randy Holmes-Farley

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But what actually gets injected into the ICP-MS?

0.22 μ filtered solution of slurry? Acidification of skimmate slurry to dissolve preciptates followed by 0.22 μ filtration? Not sure what’s being measured and therefore not sure if we are seeing the whole picture of what a skimmer is removing.

Yes, I asked Christoph if solids remain. Awaiting an answer. :)
 

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