Experiment: Trace Element Limitation in Reef Tank?

[Randy Holmes-Farley]

I'll just point out that no one has yet suggested Strontium as a possibly depleted element that would limit growth, despite its popularity in products sold for reefers to dose. hmmm.....

I expect it won’t, but I ignored it since it isn’t a trace element, and I focused on those that are. [emoji3]

 

[Hans-Werner]

The only function of strontium is its incorporation into the skeleton. There it might have a function in the formation of aragonite as the calcium carbonate modification but I´m not sure about that. Fact is that strontium mainly gets incorporated into aragonite (in contrast to calcite) skeletons since the diameter of its ion is bigger than the diameter of the calcium ion.

 

[Mortie31]

The only function of strontium is its incorporation into the skeleton. There it might have a function in the formation of aragonite as the calcium carbonate modification but I´m not sure about that. Fact is that strontium mainly gets incorporated into aragonite (in contrast to calcite) skeletons since the diameter of its ion is bigger than the diameter of the calcium ion.

My strontium is always low on my ICPs, does your explanation above mean that it is important or not? Is it skeletal incorporation vital or will it simply be replaced by something else, sorry for the dumb question I’m not a chemist

 

[Hans-Werner]

There are no dumb questions. I have not done any experimentation on strontium so I don´t know. What aquarists describe when they have done experimentation with high dosages of strontium are brittle weak skeletons. It sounds a bit like coral growth under high phosphate concentrations. Are there maybe interactions with phosphate?

Do you think the growth of your stony corals is reduced or normal? Are the skeletons brittle or hard and sturdy? What do you think?

 

[Mortie31]

There are no dumb questions. I have not done any experimentation on strontium so I don´t know. What aquarists describe when they have done experimentation with high dosages of strontium are brittle weak skeletons. It sounds a bit like coral growth under high phosphate concentrations. Are there maybe interactions with phosphate?

Do you think the growth of your stony corals is reduced or normal? Are the skeletons brittle or hard and sturdy? What do you think?

The corals seem fine, I guess it’s one of the drawbacks of ICP testing, we can chase numbers assuming their recommendations and levels are correct. Do you know if the levels recommended by triton are at or about NSW levels?

 

[Randy Holmes-Farley]

The corals seem fine, I guess it’s one of the drawbacks of ICP testing, we can chase numbers assuming their recommendations and levels are correct. Do you know if the levels recommended by triton are at or about NSW levels?

Which ones? Some are close to NSW and some are not.

I give 35 ppt NSW levels here:

What is Seawater? by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2005-11/rhf/index.php

 

[Bouncingsoul39]

Is growth in (some) reef tanks governed by trace element limitation (sometimes)?
Maybe? Probably?
The argument goes like this. If all macro nutrients are provided in abundance without care taken to replace the undetectable trace elements, then eventually some crucial scarce resource will be depleted to the point that growth slows. I should probably call these "micro-nutrients" instead of trace elements, because the limiting factor may not be an element per se, but perhaps some vitamin etc that is scarce and crucial.
Straightforward, but showing that this actually happens is a different thing.
I am keeping my tank replete in the macro nutrients: N, P, (in my case Si), Ca, Alk, Mg, and making sure my inputs of these nutrients stays absolutely consistent. Then measure anything informative I can measure to track growth in my system. In theory, if a micronutrient becomes limiting then the consumption of the macro nutrients should slow or stop, and their levels should rise with the same inputs.
Questions:

• Can growth be shown to slow dramatically in a tank with all major nutrients provided in abundance due to a depletion of micro nutrients?
• Can the limiting micro nutrient(s) be identified?
• Can the organism(s) being limited be identified?

So I started by measuring everything on day 1 and dosing all the micronutrients I could think of. After 2 weeks - here's data so far and a few comments.

Line is a 2-day average of readings. NO3 I divided by 100 so it could all be on the graph. Not all 3 are precisely comparable. NO3 has huge error bars compared to the others, It's not necessarily steady at 10 - I just can't tell between 10 or 7 or 15ppm. Also it wasn't really moving opposite the other two the first few days, I just dosed more NO3 first few days to get it up to 10.
Si may look like consumption is slowing but it's not. Here's another graph showing same nutrients with the daily addition/consumption...

I'm upping Si dose 10% a day until I get to 1 ppm Si. I find it weird that Si consumption is increasing almost exactly at the same rate as the dose increase and drops back to near the exact same level every day. I'll redo this graph when I figure out how to calculate and show the food inputs of my 2 cubes a day to P & N.
One last graph - Ca, Alk, and pH. I had to scale the Ca weirdly to fit on the graph.

Final comment on the data for now - Most everything moved as expected for days 1-5. After adding a bunch of trace elements, the consumption generally increased. At first I thought the leveling out and the rise from day 6 to 9 was the onset of the limitation, but a likelier explanation is that days 7,8 & 9 we had cold cloudy weather, and my tank gets a few hours of natural morning sunlight from a window. Sun comes back out day 10 and following and growth pics back up.

You can be the Tom Barr of reefing. Since I learned of EI dosing and Bar's theory of limitations, I had always wondered why it hasn't been applied or tested in reefing. I've always thought EI was a wasteful, expensive method of dosing though, so never used it in my planted tanks. With planted tanks, I had always wished we had what exists in reefing which is NSW params to use as a guideline. For example, in a planted tank you would shoot for 5ppm nitrate, .5ppm Phosphate etc. As far as I know, nothing like that exists. People dose an amount and wing it or do EI.

 

[taricha]

I'm glad we're reaffirming there are no dumb questions. Now I can ask why Randy says I and Sr aren't trace elements.
They're on the periodic table - I checked!
Are they not trace because they aren't scarce? Or because they don't fall into the bioinorganic chem field Hans mentioned - organic chem instead?

 

[Randy Holmes-Farley]

I'm glad we're reaffirming there are no dumb questions. Now I can ask why Randy says I and Sr aren't trace elements.
They're on the periodic table - I checked!
Are they not trace because they aren't scarce? Or because they don't fall into the bioinorganic chem field Hans mentioned - organic chem instead?

It’s the “trace” part of trace element that they do not meet. They are much too plentiful to qualify.

Seawater elements are usually divided into Major, Minor, and Trace Elements.

Major elements are often defined as 50 uM and up, minor are 0.05 to 50 uM, and trace are below 0.05 uM.

Iodine is present at 0.4 uM, so it is a minor element.

Strontium is present at 90 uM and is a major element.

For an element with a molecular weight of 100 grams per mole, then 0.05 uM of that element is 100 x 0.05 umole/L = 5 ug/L.

 

[mcarroll]

Great thread @taricha – gathering some great comments!!!

Can growth be shown to slow dramatically in a tank with all major nutrients provided in abundance due to a depletion of micro nutrients?

Good question!

My aproach

I don't remember seeing this linked anywhere before. Was it kept secret only to subscribers?

Very very interesting in an already-intereseting thread! Thanks for posting it!!

 

[taricha]

no kidding @mcarroll really quality stuff here from everyone.
Let me toss out some ideas about nutrient correlations and maybe or maybe not causations, and see what others thinking is.
A few possible changes that would make me look closely at specific groups of organisms.

If my Si moves along with N & P, I'm going to look carefully at diatoms.
If my Si moves disconnected from N & P, I'll look more at sponges than diatoms.
If N & P move alone I'll look at my algaes first.
If my Ca & Alk move, I'll look at coral/coralline calcifying organisms.

If everything moves I'll see why my salinity is off
Any other things here that would be measurable and point toward some organisms more than others?

What would we expect K might move with? I was thinking of it with N & P as mostly algae consumed.
And should Mg be expected to track with Ca/Alk during calcification?
If I'm reading these numbers right...
https://www.advancedaquarist.com/2003/10/chemistry#section-1
...coral skeletons being generally under 1% Mg and Mg being so high anyway that I suspect I wouldn't be able to measure movement in Mg from calcifying (at least not until Ca/alk had really changed.)
In fact, from the values in the table, I'm guessing the only thing movement of Mg would tell me is that there's precipitation?

 

[NY_Caveman]

no kidding @mcarroll really quality stuff here from everyone.
Let me toss out some ideas about nutrient correlations and maybe or maybe not causations, and see what others thinking is.
A few possible changes that would make me look closely at specific groups of organisms.

If my Si moves along with N & P, I'm going to look carefully at diatoms.
If my Si moves disconnected from N & P, I'll look more at sponges than diatoms.
If N & P move alone I'll look at my algaes first.
If my Ca & Alk move, I'll look at coral/coralline calcifying organisms.

If everything moves I'll see why my salinity is off
Any other things here that would be measurable and point toward some organisms more than others?

What would we expect K might move with? I was thinking of it with N & P as mostly algae consumed.
And should Mg be expected to track with Ca/Alk during calcification?
If I'm reading these numbers right...
https://www.advancedaquarist.com/2003/10/chemistry#section-1
...coral skeletons being generally under 1% Mg and Mg being so high anyway that I suspect I wouldn't be able to measure movement in Mg from calcifying (at least not until Ca/alk had really changed.)
In fact, from the values in the table, I'm guessing the only thing movement of Mg would tell me is that there's precipitation?

I am no chemist. As far as K, though, I cannot help but think of my past planted tanks where K was related to N and P. Gardening also incorporates the three in almost any fertilizer. So it seems it may be related in reefs as well in my limited understanding.

 

[Randy Holmes-Farley]

I am no chemist. As far as K, though, I cannot help but think of my past planted tanks where K was related to N and P. Gardening also incorporates the three in almost any fertilizer. So it seems it may be related in reefs as well in my limited understanding.

Potassium is higher inside cells than in seawater. Maybe 10-30 times as high. So depletion is not rapid as cell tissue grows.

The curious thing is potassium in cells in foods is equally high, so it’s not clear why it ever depletes, except that reef foods may be processed in ways that lose some of the potassium (like rinsing them after cell membranes are broken).

 

[mcarroll]

As far as K, though, I cannot help but think of my past planted tanks where K was related to N and P. Gardening also incorporates the three in almost any fertilizer. So it seems it may be related in reefs as well in my limited understanding.

Good thought.

I suspect that's related to a lack of "feeding" for the typical field or garden...we're trying to substitute for more of the natural process on those fronts than in a functioning reef tank so more comprehensive supplementation would be a given. Most tended ground is entirely dysfunctional with an extremely low number of life forms (big and small) and low levels of stability and high levels of problems with "pest organisms". Just like most new tanks. Contrast with mature healthy tanks, or functioning reefs or forests.

Anyway, if we fed our gardens (some do. see "lasagna composting" for one example) it's unlikely we'd observe the same nutrient deficiencies as we currently do – even macro nutrients such as K.

 

[Hans-Werner]

The corals seem fine, I guess it’s one of the drawbacks of ICP testing, we can chase numbers assuming their recommendations and levels are correct. Do you know if the levels recommended by triton are at or about NSW levels?

One thing I was wondering about in another thread is that the calcium level of 406 ppm marked red is in fact very close to natural seawater level while the recommendation is slightly above NSW level. The NSW level is around 410 ppm. So I would give green light to a span of at least 400 to 450 ppm calcium.

 

[Hans-Werner]

I am no chemist. As far as K, though, I cannot help but think of my past planted tanks where K was related to N and P. Gardening also incorporates the three in almost any fertilizer. So it seems it may be related in reefs as well in my limited understanding.

In reef aquaria there is not a lot of K consumption. Maybe some red and green algae incorporate some potassium. I think there is little depletion of K in reef tanks. The incorporation of major amounts of K into biomass is quite typical for land plants which freshwater aquarium plants belong to. In most freshwater aquaria plants are removed regularly. In most reef aquaria there is no similar removal of plant biomass maybe except aquaria with algal filtration. In comparision with freshwater aquarium water there is a ca. hundredfold concentration of K (4 ppm vs. 400 ppm) in reef aquarium water. So the proportion of K removed with algae is still small.

 

[taricha]

In line with last comment, I'm exporting 50 to 150g of wet weight macroalgae every 3-4 days, and have seen no K change in the occasional tests I've done. (Imports 1g kno3 most days)

I was curious if there was another test out there that might let me check Iodine. This question and answer posted on Hanna iodine page seemed worth sharing.

"Q: Can this be used for saltwater in a marine aquarium?

Answers (1)

Hanna Instruments

A: The HI718 uses DPD to react with iodine as an oxidizer to produce a pink tint in the sample. Any other oxidizers present including ozone or bromine, will cause a positive interference. A closely related product, chlorine photometer that also uses DPD, stated additional mixing time for chlorine determination in saltwater. The same would apply for Iodine. The biggest concern is the expected values. The accuracy of the meter is +/- 0.1 ppm +/- 5% of the reading. This means a 0.1 ppm reading can be anywhere from 0 to 0.2 ppm. Seawater typically is around 0.06 ppm, which is much less. If the expected value is less than 0.1 ppm then we would not recommend the meter for this particular application."

Edit: and my iodide supplement bottle recommends an amount that I calculate would only add 0.02 ppm. So it wouldn't be detectable even immediately after dosing.

 

[mcarroll]

I had some luck testing Iodine with Seachem's kit...

MultiTest™: Iodine/Iodide

• Catalysis based, sensitive to less than 0.0025 mg/L
• Multi-cavity plate for simultaneous testing of up to 6 tests at the same time
• Includes reference for test validation
• Marine or Freshwater

...back when I started ('06? '08?), but I would have to do a 6x test and use the provided reference to get an intelligible result, and even then I was left wondering sometimes.

Ultimately I gave up testing or dosing I due to the bother and lack of any apparent effect of I-dosing on the tank, but I will say that Seachem was amazing in supporting their test kits. When I quickly ran out of reagents the first time and called them to see if I was doing something wrong, they not only helped with that, but they sent me another set of reagents and told me to call if I needed more....which I did....which they sent without question. I like Seachem.

BTW, here's the one and only Q&A on their FAQ:

Q: Why am I not showing any iodine/iodide when I test? I am adding it regularly.
A: Iodide is rapidly dissipated in an aquarium. Many iodine supplements are inadequate to raise iodide to near sea water concentrations. To validate your kit use the included reference or prepare a known concentration from an iodide source at a specific concentration, such as Seachem’s Reef Iodide.

 

[Josh Kraft]

I think I accidentally kinda used my phone like one. I spent too long trial and erroring with this, but I like the result. Short version is, Phone camera -> photoshop color analysis -> graphing/statistical software -> smashing together of the results for R G and B with some ugly math and here we go:
Stock NO3 solutions I tried to mixed to 5, 10, 15, 20, and 40 ppm...
I photo test them and get 5.27, 8.78, 14.4, 19.4, and 37.4 ppm respectively
I'll take it.
Today's color of pink calculates to 12.9

There is an android app called aquarium note where you take a pic of your test and the result card, and it tells which color it is closest to

 

[Mortie31]

In my latest triton ICP my Si levels are low 21ug/l against the setpoint of 100ug/l is Si important as I read Taricha monitoring it? I keep an SPS reef.
Thank you all for posting the articles and comments, I must admit a lot of it goes over my head, but I may get it one day and it’s great to have the articles for reference