Oceamo Skimmate Analysis Results Discussion

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Randy Holmes-Farley

Randy Holmes-Farley

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Let's see if that works out.


Copper 157 ug/l in skimmate
export 0.006 ug/L/day

Either he means there was only 0.04 ml of skimmate per day

or, say,

10 ml of skimmate and the tank size was 262 L
 

sixty_reefer

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Which study are you asking about? If it is the skimmate study, its from the ICP of the digested skimmate generated each day.
IMG_3579.jpeg
IMG_3578.jpeg


Just trying to understand the results of this, I’m just curious if the 0.0010 mg/l calculated phosphate is in relation to the skimmate volume of 0.658 l or full tank and also how is it calculated
 

BeanAnimal

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Calcium binds to organics, but most notably, there is known to be calcium carbonate particulates in skimmate that will dissolve in the acid treatment, giving calcium a seeming false high reading. Same for other ions in that calcium carbonate, such as magnesium.

Most of the transition elements (iron, copper, etc.) will bind to organics which themselves bind to air/water interfaces, so they can be selectively removed by skimming even when the bare ions would not skim out.

Skimmate will also contain whole organisms such as bacteria and phytoplankton that may mostly dissolve into an acid treatment, releasing their contents for analysis, which needs to be considered at least when thinking about how ions such as phosphate or vanadium or many others show up.
IMHO - These are extremely important points that people should keep in context-- especially the organism contributions in the context of what is being "removed" and its actual effect in the system vs perceived effect based in removal values. I hope I am not being confusing.
 
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Randy Holmes-Farley

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IMG_3579.jpeg
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Just trying to understand the results of this, I’m just curious if the 0.0010 mg/l calculated phosphate is in relation to the skimmate volume of 0.658 l or full tank and also how is it calculated

Christoph will have to say for sure, but it only makes numerical sense, IMO, if it is per L of tank water from the calculation I did above.
 

Dan_P

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I expect (hope) that is what Christoph used to determine export in ug/L/day in the lower set of data. :)

I await further transparency (this should be a great discussion. The data is interesting already).
 
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Randy Holmes-Farley

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IMHO - These are extremely important points that people should keep in context-- especially the organism contributions in the context of what is being "removed" and its actual effect in the system vs perceived effect based in removal values. I hope I am not being confusing.

Yes, agreed. If those "exports" are already inside of bacteria, it is effectively removed anyway unless something eats a living or dead bacteria and recycles the elements.

One other implication of my comments, which is probably not what you were driving at, is that one cannot export nonliving organics without taking these ions with it (although one may be able to get them consumed in the tank, possibly releasing the elements). Whether it is by skimming, GAC, purigen, water changes, or anything else, the export of the organics drag other stuff with it.
 

Christoph

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Hi everyone,

I don’t have a water analysis result for this particular tank from the same timeframe. However, I do have “matched pairs” of tank water/skimmate analyses and will prepare some to share when time permits.

Why are we conducting skimmate analyses?

The primary reason is that, in my opinion, skimmate acts like a “chemical memory” of a tank. For instance, a pulse dosing of copper (where a high dose is added at a singular time point) might be missed in regular ICP analyses depending on the sampling time. This is because copper levels drop quickly, also due to precipitation. These precipitates accumulate in the skimmate, making the “copper pulse” detectable even after it has been largely removed from the water column.

In general, we don’t observe significant accumulation of macroelements in skimmate; their concentrations usually reflect the tank’s concentrations. However, this isn’t the case for many trace elements and phosphorus, where concentrations are often much higher in the skimmate. The most likely reasons for this include:

  • Binding to organics, followed by skimming
  • Uptake by bacteria/phytoplankton and subsequent skimming
  • Precipitation, followed by skimming
Example Calculation: Export Rates (using random numbers)

Let’s assume a tank has a net volume of 1,000 liters and collects 500 mL of skimmate over 5 days.

The nickel concentration in this skimmate is determined to be 1,000 µg/L.

Since the skimmate volume is only 0.5 liters, the total mass of exported nickel is:
1,000 µg/L × 0.5 L = 500 µg

This means 500 µg of nickel was exported over 5 days. Dividing by 5 gives a daily export rate of:
500 µg ÷ 5 days = 100 µg/day

Given that the tank has a volume of 1,000 liters, the daily nickel export rate per liter is:
100 µg ÷ 1,000 L = 0.1 µg/L/day

We are reporting those rates to (hopefully) make the results better compareable between tanks.


All the best, Christoph
 

Christoph

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I'd be cautious in interpreting that data. The intent was, I'm sure, to readily see what was and was not bound, not how much in typical use. As I'm certain Christoph will attest, the amounts of media used were very large. For a 100 gallon aquarium, its akin to 10 gallons of media.

Then 10 bed volumes of sample solution (natural seawater, partly with element spikes) were slowly allowed to drip through the media bed.
Exactly. These "reactor media" tests were conducted using high adsorber amounts relative to the volume of seawater used. The aim was to demonstrate all potential effects of the material.

I completely agree that these results are not always fully transferable to a "real-life" reef tank scenario. However, we do observe most of these effects in actual tanks as well. For example:

Vanadium levels if reef tanks use GFO (mean = 1,49 µg/l), vs reef tanks that do not use GFO (mean = 4,28 µg/l)

1737666967422.png
 

FernBluffReef

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goal here? To understand what elements may be stripped by skimming? Agreed with others would be necessary to know the levels of the source water to make any solid conclusions I’d think?

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.

For example was the skimmate from an ULNS and as such these levels are far higher then the source water or is skimmate not near as rich as we might think / want to think?

Following to learn more
 

Christoph

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Is the skimmate that is sent in for testing everything from the skimmer cup, all fluid and the solid buildup in the neck & cup?
Noteworthy this is not a routine test available directly from the shelves. We have conducted this "SkimQuant" Analysis in a limited number of cases for troubleshooting and to gain information.

The point you raise is very significant, the skimmate is not a homogenous mass, so the sampling becomes even more important. 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.

BR, Christoph
 
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Lasse

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For example was the skimmate from an ULNS and as such these levels are far higher then the source water or is skimmate not near as rich as we might think / want to think?

It was surly not an UNLs tank - from here
1737702002361.png


And note - from post 1 in this thread

1737703077388.png

As I understand it - correct me if I´m wrong - the export rate is calculated from atomic P - it include even P bound in the accumulated biomass of skimmer cup bacteria. The export rate is around 0.8 % of the PO4 content of the water - probably a little lower because the organic phosphorus is filtered out in a photometric phosphate analyse.

Sincerely Lasse
 
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Hans-Werner

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Shouldn't the only enriched species in the water should be proteins and their chemical species?
The purpose of a protein skimmer is too remove proteins. I don't see where iron or TA or calcium, etc would be enriched in the skimmate. Most species listed are not even hydrophobic and so won't stick to the bubble surface.

I think that it is fairly evident with the color of the skimmate on how well the skimmer is working.
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.
 

Doctorgori

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It would be very interesting to expand this to trace element dosing or not: maybe even adapt/adjust it based on skimmate results …
Anyway as a non scientist I cant honestly discern exactly what Im reading on a ICP test if I were being honest
 

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