Experiment: Trace Element Limitation in Reef Tank?

[taricha]

Any updates on this? I was just looking through this thread and found the whole discussion about trace elements interesting.... debating trying to supplement them in my tank

Still playing with it. On my personal tank, between vacation travel and an A/C disruption where tank got hot, I'm just now getting it back stable. I'll then test the Iron supplement part of Red Sea Trace Colors. I'll be looking at different things than he did, but check @Brew12's documentation in post #134 on Fe supplementation increasing Algae fuge performance as indicated by 24-hr pH monitoring.

I'll try to post details later, but the levels of Iron that occur in NSW are below what ICP can detect, and the levels we can test with hobby kits, and therefore the levels that Red Sea recommend are several orders of magnitude larger than natural. All that said, if a tank has N & P provided consistently replete, then I'd bet that Fe is most likely a limiting nutrient to the growth of something.
What's limited? Algae - almost certainly. Corals - maybe
Is this limitation met by enriched fish foods, or premium 2-part/3part, or other additives? I suspect that varies considerably from tank to tank.

 

[taricha]

wanted to come back to Iron dosing & testing, since I'll be adding Fe in a couple of days.

For some reason, my system likes to become iron limited. I had gone a few weeks without dosing iron or doing a water change and once again, my chaeto stopped growing and my nutrients started climbing. This can be seen in my pH graph. Once I added an iron supplement on Jun 9th my fuge was once again more effective at limiting my pH drop overnight. My NO3 and PO4 is also declining.

I should be able to get more understanding on how my system consumes iron now that I have a test kit for it.

Maybe. Maybe not.
from Randy's article: Chemistry And The Aquarium: Iron In A Reef Tank
Typical Iron concentration in ocean surface water may be on the order of 1 nanomolar, or 0.000006ppm (in ppb it's only 0.006 if that looks any better). At those low levels it's almost certainly limiting to many things.
If you send in a sample to get an ICP test, the limit of detection for Fe according to Triton is between 0.31-1.4ppb - let's ballpark it at 0.6 ppb so we can say it's ~100 times higher than NSW.
Hobby test kits - hanna makes a Low Range Iron checker that they say not to use for Saltwater (but says is based on an adaptation of the TPTZ method - which google says it can be used in saltwater) claims +-20ppb so ~5,000 times higher than NSW.
Red Sea Fe test kit claims limit of detection 0.05ppm = 50ppb or ~10,000 times higher than NSW.
And now we get to Red Sea Trace Colors C (iron+) recommended Fe dose of 0.15ppm = 150ppb so ~30,000 times higher than NSW.
Why do they recommend levels 4+ orders of magnitude higher than NSW? Is it just because that's the level that their kit can test for?

Red Sea’s Iron Pro test kit is an advanced colorimetric test, measuring the level of total Iron (chelated and non-chelated iron) to an exceptionally high accuracy of 0.05 ppm. This test kit enables the accurate dosing of Trace-Colors™ Iron+ supplement.

...maybe so.

I'm genuinely curious on a few things here.
Red sea also talks about possibility of overdose.

Toxic to all invertebrates above recommended levels. Common indication of overdose is a darkening of the corals due to excessive Zooxanthellae growth and the outbreak of nuisance algae. Can cause regression of the soft tissues in SPS corals. In case of over dosing change 50 % of the water and reduce the supplementing dosage by 50%.

seems weird to me that 30,000 times natural levels is ideal, but at 2 or 3 times that much, things start to go sideways? totally possible, but puzzling.

And the other thing I'm curious on is the pathway by which a tank can go from thousands of times higher than natural levels down to biologically limiting levels - if that indeed happens - in a "few weeks" as Brew12 said.
some of the different mechanisms are discussed here...

Iron will be both taken up and precipitated from the water as insoluble iron oxide. It is taken by by every organism as it grows, but algae of all types can take up quite a bit and are the species that most commonly appears to suffer from depleted iron [....]

Iron also is likely bound to organics in reef aquaria, and those organics can be skimmed out or bound to GAC. Bacteria take up iron as they grow, so organic carbon dosing will also boost the loss rate of soluble iron.

If iron really depletes that much that fast, I wonder which of those mechanisms are dominant? biological or abiotic? I'm not sure how one would go about trying to figure that out, but I'll think about it.

And a final thought - I'm usually talking about possible Fe (and other trace element) limitation as a growth inhibitor - of something. And interested in the idea that perhaps tanks that get fantastic growth and coral health have ways of providing Fe, but the counterpoint from @Jose Mayo in his thread: Could it be iron, the great hidden enemy of reef aquarists? is that Fe also fuels nuisance growth, and maybe the systems with great coral health are the ones that have ways of keeping Fe relatively depleted.

 

[mcarroll]

Seems to me like bacteria would be required to keep Fe in ultra-low concentration by way of siderophores, which (maybe?) would skew iron availability to heterotrophs that can eat the bacteria to acquire the Fe?

(Whenever there's an apparent mystery, first ask how microbes have been overlooked. Saw something to that effect in a paper once.)

 

[taricha]

(Whenever there's an apparent mystery, first ask how microbes have been overlooked. Saw something to that effect in a paper once.)

That's great! Much better than my internal motto - "Ignore bacterial effects until it's impossible to keep ignoring them."

Also had a similar thought along these lines - brew12 says his iron seems to deplete unusually fast, every few weeks.
He also uses vibrant on maintenance dose every two weeks. Not clear if his iron depletion rate is actually unusually fast compared to others, or if there's any connection to vibrant, but interesting to think about.

 

[dragon99]

Great info in this thread and timely because I've been wondering about trace elements more lately. Keep it up!

 

[taricha]

Finally! Here's what it looks like when I dose trace elements that have been limiting in my system.

This is a graph of the day-to-day consumption of PO4-blue, NO3-red, SiO2-yellow, and Alk-green.
100% on the graph represents the long term average consumption per day for each parameter over the whole experiment. The long term average of each is listed on the graph.

• SiO2 consumption increased roughly +70%

(NO3 and PO4 consumption had settled down to around 70% of long term average before dosing. After dosing they both increased to above 100% of the long term average.)

• NO3 was up roughly +50%
• PO4 was up roughly +40%
• and Alk (calcification) was the smallest increase, only up around 15-20%

the Alk is the smallest increase, and perhaps not real. It is the most carefully measured, but I'll wait to see if the trend reverses absent dosing before concluding things for certain.

The one effect I did not find, that @Brew12 tracked was there is no pH increase. pH measured at lights on was 8.05-8.10 every day.

maybe my tank aeration suppressed any pH change? Dunno.

 

[Brew12]

he one effect I did not find, that @Brew12 tracked was there is no pH increase. pH measured at lights on was 8.05-8.10 every day.

Very interesting!

I've been on vacation without internet access, so lots to catch up on. Just to clarify, my pH didn't really rise much. It just didn't drop as much at night when my reverse light cycle fuge was lit.

 

[Randy Holmes-Farley]

Interesting. Clearly, diatoms like it.

 

[BestMomEver]

I don’t have time to read 8 pages of posts so I’m sorry if this question has been asked... but I have a bottle of trace elements that I’ve never used. Basically because I’ve been afraid to do it. My adage has always been, “if you can’t test for it, you shouldn’t dose it.” But, I know it’s manufactured for a reason. If I’m doing monthly 10% water change and dosing kalkwasser, would it be necessary?

 

[taricha]

I don’t have time to read 8 pages of posts so I’m sorry if this question has been asked... but I have a bottle of trace elements that I’ve never used. Basically because I’ve been afraid to do it. My adage has always been, “if you can’t test for it, you shouldn’t dose it.” But, I know it’s manufactured for a reason. If I’m doing monthly 10% water change and dosing kalkwasser, would it be necessary?

Good Q. hopefully, this thread can get closer to an answer.
Right now I think what's clear is that if you have algae fuge or scrubber and its growth is slow, stalled, or not what you expect based on NO3 and PO4 in the system, then yes - you should dose trace elements.
If you are fighting or have recently fought nuisance algae - dinos, diatoms etc. then definitely don't.

For everyone else right now it's an open question, but what I've seen so far - I'd lean toward trying it and observing the system carefully.

 

[taricha]

Interesting. Clearly, diatoms like it.

Totally. Weirdly the sand is only slightly more pigmented - I keep expecting a "bloom."
My immediate questions I look to answer next at this point are
1 - how long for system to return back to basically pre-dose consumtption rates?
2 - is it repeatable? same dose get same effect?
3 - deplete Silica (should only take under a week), try dosing the same trace in a no-Si environment like most tanks. See what the response to dosing is under those conditions.
4....
5....

 

[Randy Holmes-Farley]

Totally. Weirdly the sand is only slightly more pigmented - I keep expecting a "bloom."
My immediate questions I look to answer next at this point are
1 - how long for system to return back to basically pre-dose consumtption rates?
2 - is it repeatable? same dose get same effect?
3 - deplete Silica (should only take under a week), try dosing the same trace in a no-Si environment like most tanks. See what the response to dosing is under those conditions.
4....
5....

So much to figure out, and so few reef tanks to try it on.

 

[taricha]

*whispers* Yall, I think the calcification increase may have been real. ;Wideyed
Alkalinity consumption is the green line. Dosing started after testing on day 67.

 

[BradB]

I run a 270 gallon display with relatively few water changes. I have noticed increased growth after a water change, even if parameters were in line before. But it usually growth of something I don't want, hair algae, etc. I've always attributed it to stuff being stirred up and getting a small nutrients spike, but missing trace elements makes more sense. I don't get the same affect if I just stir everything up without changing water.

 

[vetteguy53081]

This is interesting. I was struggling with how do you know when to start adding trace elements to a tank. But this will help with the second part of the question which is will it make a difference.

In between water changes

 

[taricha]

Ok. Thought I'd update this, now two weeks after stopping Trace element dosing. Check it out.

The data is a little bumpy, uncertainties are stubborn things - also day 72-74 were cloudy, and my sunlit tank got less light, so you can see the effect there...
BUT all measurable nutrient consumption rates increased in response to the application of Red Sea Trace Colors C (Iron+), and now we can see the post dosing decrease as well.

The alkalinity (and by proxy calcium) increase is the smallest, but also the most interesting/desirable, and most carefully measured.
a closer look at Alk alone.

The calcification increase in response to Trace metal (Fe) dosing is small but real. I think that's pretty cool.
My takeaways at this point are that...
1) Trace elements can become limited in a system if N,P,Ca,Alk etc are kept replete.
2) Looks very much like Fe is the most likely candidate for limitation in the trace cocktail.
3) dosing Iron (in the red sea recommended approach) appears to increase the consumption rates (and inferring from that increased growth rates) of seemingly all photosynthetic classes: diatoms, microalgae, macroalgae, and even calcifying corals.
4) two weeks after dosing, the consumption rates of all nutrients have seemingly dropped down from their post-dosing peaks, but are also still clearly higher than their pre-dosing Fe-limited levels.

That's what it looks like to me so far.
in a later post I'll talk about some observations of what's changed in the tank.

 

[taricha]

So aside from measuring chemistry, I also noticed some big responses in small things in the tank after dosing Trace (Fe).
Six days after I started dosing, I noticed a bunch of hydroids on the glass. I've had one or two before, but this was a much larger number, more densely packed than I've ever seen in my tank.

(a tiny patch of hydroid bloom)
And if there's a bloom of hydroids, there must be.....

Yep, a bunch of copepods. Also in denser numbers than I'd ever seen in my tank.
And all those white dots around the copepods, I thought they may be copepod nauplii, but looking closer - they are mass numbers of ciliates.

So here's the thing - none of those things (hydroids, pods, ciliates) have a direct use for Fe dosed into the water - they all must be supported by it indirectly. Something like this....

So even though the hydroids are several trophic levels away from anything that can directly take up Fe from water, it only took 6 days after dosing for them to bloom.
Now, 2 weeks after the initial Hydroid bloom, their numbers still haven't gone down much, indicating that this food web that appeared after dosing trace elements hasn't yet totally collapsed.
If this food web boosts hydroids on the glass, it's quite likely that corals could be seeing similar benefits.

Finally, one of the claimed reasons that people should dose this Trace element product, is that these elements are beneficial in corals forming green fluorescence. My green corals were looking a little faded, so I figured I'd document, just in case.

The corals definitely look more intensely green to the eye, and the camera captures some of that.


Edit: also to reiterate, adding trace elements to system that was already replete in major nutrients apparently boosts ALL classes of photosynthesizers.
So my GHA patches (derbesia) have really taken off.
Someone without appropriate herbivores up to the challenge would probably find it to be a failure to be avoided - despite the small positive changes I've cited.

 

[Rick Mathew]

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.

I do appreciate all this effort to add to our understanding of Reef Chemistry...excellent work

 

[vetteguy53081]

So aside from measuring chemistry, I also noticed some big responses in small things in the tank after dosing Trace (Fe).
Six days after I started dosing, I noticed a bunch of hydroids on the glass. I've had one or two before, but this was a much larger number, more densely packed than I've ever seen in my tank.

(a tiny patch of hydroid bloom)
And if there's a bloom of hydroids, there must be.....

Yep, a bunch of copepods. Also in denser numbers than I'd ever seen in my tank.
And all those white dots around the copepods, I thought they may be copepod nauplii, but looking closer - they are mass numbers of ciliates.

So here's the thing - none of those things (hydroids, pods, ciliates) have a direct use for Fe dosed into the water - they all must be supported by it indirectly. Something like this....

So even though the hydroids are several trophic levels away from anything that can directly take up Fe from water, it only took 6 days after dosing for them to bloom.
Now, 2 weeks after the initial Hydroid bloom, their numbers still haven't gone down much, indicating that this food web that appeared after dosing trace elements hasn't yet totally collapsed.
If this food web boosts hydroids on the glass, it's quite likely that corals could be seeing similar benefits.

Finally, one of the claimed reasons that people should dose this Trace element product, is that these elements are beneficial in corals forming green fluorescence. My green corals were looking a little faded, so I figured I'd document, just in case.

The corals definitely look more intensely green to the eye, and the camera captures some of that.


Edit: also to reiterate, adding trace elements to system that was already replete in major nutrients apparently boosts ALL classes of photosynthesizers.
So my GHA patches (derbesia) have really taken off.
Someone without appropriate herbivores up to the challenge would probably find it to be a failure to be avoided - despite the small positive changes I've cited.

Wow- Huge difference!

 

[Brew12]

So aside from measuring chemistry, I also noticed some big responses in small things in the tank after dosing Trace (Fe).
Six days after I started dosing, I noticed a bunch of hydroids on the glass. I've had one or two before, but this was a much larger number, more densely packed than I've ever seen in my tank.

(a tiny patch of hydroid bloom)
And if there's a bloom of hydroids, there must be.....

Yep, a bunch of copepods. Also in denser numbers than I'd ever seen in my tank.
And all those white dots around the copepods, I thought they may be copepod nauplii, but looking closer - they are mass numbers of ciliates.

So here's the thing - none of those things (hydroids, pods, ciliates) have a direct use for Fe dosed into the water - they all must be supported by it indirectly. Something like this....

So even though the hydroids are several trophic levels away from anything that can directly take up Fe from water, it only took 6 days after dosing for them to bloom.
Now, 2 weeks after the initial Hydroid bloom, their numbers still haven't gone down much, indicating that this food web that appeared after dosing trace elements hasn't yet totally collapsed.
If this food web boosts hydroids on the glass, it's quite likely that corals could be seeing similar benefits.

Finally, one of the claimed reasons that people should dose this Trace element product, is that these elements are beneficial in corals forming green fluorescence. My green corals were looking a little faded, so I figured I'd document, just in case.

The corals definitely look more intensely green to the eye, and the camera captures some of that.


Edit: also to reiterate, adding trace elements to system that was already replete in major nutrients apparently boosts ALL classes of photosynthesizers.
So my GHA patches (derbesia) have really taken off.
Someone without appropriate herbivores up to the challenge would probably find it to be a failure to be avoided - despite the small positive changes I've cited.

This is fantastic work! I've known my tank does better when I add Fe but this is amazing stuff.

I wish I were disciplined enough in caring for my tank to document stuff like this!