Experiment: Trace Element Limitation in Reef Tank?

[Hans-Werner]

You're welcome. Iron is a very interesting element regarding trace element supplementation. Taking into consideration how scarce iron is in seawater corals incorporate quite a lot into their skeletons. Why do they do this? There are different possible answers:
- In fact iron is not so scarce in reefs. They take it up in particular form, for example as food.
- They need it for calcification, for example for some enzyme needed for calcification.
- Corals remove iron from reef waters to make life hard for algae and cyanobacteria.
In the latter case we could doubt the sense of an iron supplementation in reef aquaria although it is depleted very rapidly just like iodine.

 

[Hans-Werner]

I finally had to look up Siderophore

There is another interesting paragraph in your link:
Related processes
... Recent data suggest that iron-chelating molecules with similar properties to siderophores, were produced by marine bacteria under phosphate limiting growth condition. In nature phosphate binds to different type of iron minerals, and therefore it was hypothesized that bacteria can use siderophore-like molecules to dissolve such complex in order to access the phosphate.[48]

I suspect that the red Oscillatoria cyanobacteria do this or something similar. They either excrete this kind of siderophore or they just excrete organic acids to dissolve phosphate from calcium phosphates or they do both. What speaks for the siderophore thing is that cyanobacteria seem to like iron dosing in reef aquaria. Do they need the iron or do they make use of the precipitated iron phosphate?

 

[taricha]

Iron and vitamin B12 are why I just don't trust cyano.
It can provide too many things that support an otherwise stalled bloom of pests, looks suspicious.

 

[taricha]

Ok, lets take a look at the first things that could maybe be called results ....
How does Iodide (Red Sea Trace Colors A) affect the consumption of major elements in my tank? I.E. was iodide limiting growth of anything in the system in a measurable way?
Iodide itself tracked over days...

Day 17: Presence of iodide (and probably other things) began to appear in tank water from decaying gorg tissue damaged a day or two earlier.
Day 22: Red Sea A added.

Now, a look at Calcium and Alkalinity consumption...
(first 10 days were stabilizing system Days 10-20 are best period of stability to use as baseline data)

Surprising! It really looks like Ca and Alk consumption was measurably higher in the period after day 22 - addition of Red Sea A, as compared to the 10 day stable baseline period from days 10-20. We'll come back to that in a bit, but let's look at N, P, and Si consumption...

Weird - unlike Ca/Alk, there's no real change whatsoever. P, N, Si seem to be consumed at almost exactly same rates during the time of provided Iodide as when it was depleted.

I think there's multiple possible interpretations of the data and I'll give my best attempt to make sense of it in the next post. I'd obviously welcome anyone else's take on it as well.

 

[taricha]

So, here's my best attempt to make sense of somewhat conflicting data.
At first glance it looks like calcification was increased after Iodide was provided, but N,P,Si consumption did not change at all. But a closer look at Ca and Alk: the Alk increase is very slight, maybe not at all. And of the two, the Ca is much higher uncertainty relative to consumption than Alk. (Ca +-5 when consumption is about 3ppm, and Alk +-0.1 and daily consumption is 0.6)
In short, if the Alk and Ca tell different stories, then trust the Alk - and it suggests a small to no effect. Which is closer to same result as the N, P, Si.
It is actually easier to make the case that there WAS a short-lived increase in consumption of all kinds, and it precedes the dosing of the red sea product, and is instead a result of the nutrients liberated by decomposing gorgonian tissue. The decomposition was first noticed on day 17, and an increase in consumption in all nutrients Ca, Alk, P, N, & Si shows up for consecutive days from 20,21,22 - so consumption of all the nutrients on day 23 is higher than on day 19. Take the Ca for instance - the largest increase follows the gorg tissue decomposition but precedes the red sea dosing. By the time the dosing came, the Ca consumption had leveled, and showed no further increases.

To sum up, I think the best interpretation of the data that I can come up with is that it shows an increase in consumption of all measured nutrients due to release of scarce resources from dying gorgonian tissue, and little to no effect on the consumption rates due to the dosing of Red Sea A.

I intend to repeat this for the other trace colors components: B, C, & D. (I'll probably follow up later and do A again without the confounding variable of the dying gorgonian tissue.)
C - Iron, Manganese, Cobalt, Copper, Aluminum, Zinc, Chrome and Nickel - is the one I'd expect to see the greatest affect on consumption rates.

 

[taricha]

so since I dose nitrate (mostly as KNO3, but switching to NaNo3 - persistently highish K.) I'm actually adding alkalinity...

In equation 2 we see that exactly one bicarbonate ion is produced for each nitrate ion consumed. Consequently, the alkalinity gain is 0.8 meq/L (2.3 dKH) for every 50 ppm of nitrate consumed.

from Alk/Ca balance article
On average, I have dosed 1.42ppm NO3 per day, which gives me 1.42*(2.3/50) = 0.065dKh added per day by nitrate. Negligible? sort of. But my daily consumption of alk is around 0.6dkh, so this is actually a 10% effect.
My tank has been receiving and consuming an extra 10% more alk than what I've accounted for from just what I was feeding it through 2part (+a little kalk).

And now that I've gone down this path I think there may be another possibly larger source of hidden alk addition... Sodium metasilicate.

The alkalinity rises because the silicate releases OH- to form silicic acid:

SiO3-- + 3H2O --> Si(OH)4 + 2OH-

I have added on average 0.240ppm of Si (0.51ppm SiO2) daily in the form of Brightwell spongexcel - sodium metasilicate. The cloudiness (Mg temporary precipitation) is about as big as when I add the 2 part, and I've seen it raise my tank pH in the ballpark of +0.10, so I'd guess it's significant.

How do I figure out the Alkalinity contribution of this Silica dosing?

 

[taricha]

This maybe wrong, but I'll take a stab at doing my own chem homework on this one.

"The alkalinity rises because the silicate releases OH- to form silicic acid:

SiO3-- + 3H2O --> Si(OH)4 + 2OH-"

I have added on average 0.240ppm of Si (0.51ppm SiO2) daily in the form of Brightwell spongexcel - sodium metasilicate. ...

How do I figure out the Alkalinity contribution of this Silica dosing?

here goes:
assume 1ppm (=mg/L) Si. change to moles Si 1mg/(28.1g/mol) = 35.6 micromoles Si. Based on above equation, 2 OH- for each Si, gives 71.2micromoles OH- per Liter.
1 millimolar of OH- = 1meq/L I think. so 71.2 micromolar OH- = 0.0712 meq/L. And 0.0712 meq/L * 2.8 = 0.199dKH

So every 1ppm Si addition raises alkalinity by 0.199dKH. (maybe?)
I'm adding 0.24ppm Si so adding (.24*0.199) = 0.048 dKH. (possibly?)

 

[Randy Holmes-Farley]

Looks like a reasonable estimate.

Not all of the silica in the tank water is silicic acid, but the net effect of anything that is actually consumed by organisms is effectively all silicic acid/SiO2 (even if the form taken up is silicate, when they take up silicate, they will release the alkalinity that came with it).

 

[taricha]

Cool!
So my daily Nitrate and Silica additions contribute 0.065 + 0.048 = 0.113 dKH which means compared to the traditional alk addition of 0.60-0.65 dKH per day - this constitutes a "hidden" additional alk input of around 18%, big enough I ought to account for it.
I need to think through my other additives and see if there's anything else hidden that's big enough to care about.

Exhaustive list of daily additions in ~75 gal:
1 cube mysis, 1 cube brine (San Francisco Bay)
the alk portion of 2 part (seachem reef fusion) + CaCl (Kent liquid calcium) for the other part, + a little kalk as needed for pH control
Sodium metasilicate (SpongExcel)
2ml vodka, 9ml vinegar
NaNo3

the vodka + vinegar is the only other thing I think is making some contribution to alk, and I can't imagine it's significant. But maybe I'll run some numbers.

 

[Randy Holmes-Farley]

the vodka + vinegar is the only other thing I think is making some contribution to alk, and I can't imagine it's significant. But maybe I'll run some numbers.

Organic carbon dosing using any neutral organic compound won't have a calculable impact on alkalinity (meaning there may be indirect effects, such as through changes in pH that impact calcification processes) but nothing you can calculate.

You'd need to dose something like sodium acetate to have a direct effect.

 

[taricha]

Ok. Great. one last comment on this line of thought...

average daily Alk consumption from day 10 to 27 of 0.63dKH - plus the adjustment from "hidden" +.113dKH - gives ~0.74dKH.
Based on 1.4dKH per 10ppm Ca, this predicts 5.28ppm Ca per day.
My actual measured Ca consumption from day 10 to 27 averages to ~5.0ppm per day.
Not bad. ~6% less measured Ca consumption than expected from calculation. And a couple of those percent could be blamed on Mg/Sr replacement.

So certainly agreement to within levels that my test kits and supplements can support.

 

[Randy Holmes-Farley]

Ok. Great. one last comment on this line of thought...

average daily Alk consumption from day 10 to 27 of 0.63dKH - plus the adjustment from "hidden" +.113dKH - gives ~0.74dKH.
Based on 1.4dKH per 10ppm Ca, this predicts 5.28ppm Ca per day.
My actual measured Ca consumption from day 10 to 27 averages to ~5.0ppm per day.
Not bad. ~6% less measured Ca consumption than expected from calculation. And a couple of those percent could be blamed on Mg/Sr replacement.

So certainly agreement to within levels that my test kits and supplements can support.

Yes, that's good agreement. I get 4.6 ppm calcium per day from a more detailed calculation, but it will vary with the magnesium incorporation.

https://www.reef2reef.com/threads/r...g-three-parameters.321163/page-2#post-3981087
from it:

"the theoretical demand ratio we calculated of

17.5 mg calcium
1.5 mg magnesium
30 mg = 1 meq/L = 2.8 dKH of alkalinity"

 

[taricha]

Yes, that's good agreement. I get 4.6 ppm calcium per day from a more detailed calculation...
"the theoretical demand ratio we calculated of

17.5 mg calcium
1.5 mg magnesium
30 mg = 1 meq/L = 2.8 dKH of alkalinity"

Excellent. So after a month i can confirm really there is no value in testing Ca daily. All that calculating Ca daily consumption independent of Alk tells me is exactly the same thing that Alk consumption tells me - just with less accuracy.
I mean, I guess that was expected, but I thought that possibly between corals, gorgs, sponges, diatoms, mollusks, algae, abiotic precipitation etc - that it was possible something somewhere consumed more of either Ca or Alk than balanced ratios.
It just doesn't happen though. They all calcify in basically the same way. And Ca/Alk always move together.
Good to know for certain. I'll only test Ca as often as needed to keep it in the 420-430 ballpark.

 

[taricha]

From another thread. This is the best quantitative evidence I've seen so far for a trace element limitation...

...
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. So while it isn't removing PO4 via precipitation, adding iron is indirectly reducing nutrients in my tank.

nutrient (NO3, PO4) levels, Chaeto growth, and pH swings - all changed direction upon addition of Iron.

Awesome, Brew12. A few Qs - any of them you could answer would be helpful.
1) what product (& how much) did you dose on Jun 9?
2) what is the daily light schedule on the fuge?
3) what are your daily inputs of foods/doses/additives etc? (what things went in your system andyou still saw an Iron limitation)
4) can we detect an increase in the daytime upswing in pH from your display - I.E. were corals Iron limited too? maybe not - they can grab food in ways algae can't. Or maybe they were but we can't detect it. Looks like we'd need a few more days either way.
5) how long would we have to watch your pH, to see it revert back to the pre Jun 9 pattern. (guess we'll have to wait)

 

[Brew12]

From another thread. This is the best quantitative evidence I've seen so far for a trace element limitation...

nutrient (NO3, PO4) levels, Chaeto growth, and pH swings - all changed direction upon addition of Iron.

Awesome, Brew12. A few Qs - any of them you could answer would be helpful.
1) what product (& how much) did you dose on Jun 9?
2) what is the daily light schedule on the fuge?
3) what are your daily inputs of foods/doses/additives etc? (what things went in your system andyou still saw an Iron limitation)
4) can we detect an increase in the daytime upswing in pH from your display - I.E. were corals Iron limited too? maybe not - they can grab food in ways algae can't. Or maybe they were but we can't detect it. Looks like we'd need a few more days either way.
5) how long would we have to watch your pH, to see it revert back to the pre Jun 9 pattern. (guess we'll have to wait)

Glad you found it interesting!

1) 40ml of Red Sea Trace Colors C
2) 6pm to 8am
3) 2 cubes PE mysis, 1/2 sheet nori, small piece of LRS Fish Frenzy daily. Occasional teaspoon of Reef Frenzy, normally twice a week.
4) The only other possible indication is that I struggle to keep corals green. I believe that is also a sign of iron limitation
5) I'm not sure. This is the first time I have actually measured how much iron supplement I have added. I also just purchased the iron test kit a few weeks ago. I'm very interested also!

 

[taricha]

Glad you found it interesting!

1) 40ml of Red Sea Trace Colors C
2) 6pm to 8am
3) 2 cubes PE mysis, 1/2 sheet nori, small piece of LRS Fish Frenzy daily. Occasional teaspoon of Reef Frenzy, normally twice a week.
4) The only other possible indication is that I struggle to keep corals green. I believe that is also a sign of iron limitation
5) I'm not sure. This is the first time I have actually measured how much iron supplement I have added. I also just purchased the iron test kit a few weeks ago. I'm very interested also!

1) excellent - I'm using same product. Trace C has lots of goodies in it. Fe, Mn, etc. Maybe down road later can distinguish between them. What's your system volume the 40ml is going into?
2) awesome. Was hoping they were reverse lit to give us a chance at separating effects on coral vs algae fuge.
3) nori! Wow. I had assumed this wouldn't happen in a tank that was getting fed seaweed. Its pretty packed with trace elements.
A few people have seen stalled dino blooms explode after feeding nori. One saw such strong correlation, he sent me some red & green sea veggies to check for dino cysts - of course there were none.

So much for things I thought I already "knew".

 

[mcarroll]

A few people have seen stalled dino blooms explode after feeding nori. One saw such strong correlation, he sent me some red & green sea veggies to check for dino cysts - of course there were none.

Could speak more to the digestibility of noori if lots of nutrients and bulk were passing through the fish vs being utilized – excellent dino-fodder; good coral food too, if circumstances are different. (And something I've wondered about.)

 

[taricha]

here's why I think nori is interesting. Stuff in nori -

Different source, different porphyra species, similar story...

Edible seaweed Porphyra vietnamensis growing along seven different localities of the Central West Coast of India was analyzed for mineral composition (Na, K, Ca, Mg, B, Pb, Cr, Co, Fe, Zn, Mn, Hg, Cu, As, Ni, Cd and Mo) by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The concentration ranges found for each sample, were as follows: Na, 24.5–65.6; K, 1.76–3.19, Ca, 1.40–6.12; Mg, 4.0–5.90 (mg/g d wt); Pb, 0.01–0.15; Cr, 0.13–0.22; Co, 0.06–0.20; Fe, 33.0–298; Zn, 0.93–3.27; Mn, 4.22–10.00; Hg, 0.01–0.04; Cu, 0.54–1.05; As, 1.24–1.83; Ni, 0.02–0.25; Cd, 0.14–0.55; Mo, 0.02–0.03 and B, 0.02–0.07 expressed in mg/100 g dry weight.

So if these trace elements can become scarce even in a system with nori being fed - then that might greatly expand the number of possible reef tanks that could be trace element limited.

 

[Brew12]

1) excellent - I'm using same product. Trace C has lots of goodies in it. Fe, Mn, etc. Maybe down road later can distinguish between them. What's your system volume the 40ml is going into?
2) awesome. Was hoping they were reverse lit to give us a chance at separating effects on coral vs algae fuge.
3) nori! Wow. I had assumed this wouldn't happen in a tank that was getting fed seaweed. Its pretty packed with trace elements.
A few people have seen stalled dino blooms explode after feeding nori. One saw such strong correlation, he sent me some red & green sea veggies to check for dino cysts - of course there were none.

So much for things I thought I already "knew".

I estimate my total water volume around 170g -180g.

One wild card is that I had a recent bout with Bryopsis that I cleared using Fluco. If I had to guess the Bryopsis takes a lot of iron out of the water and it didn't get released back into the system when it died.

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

 

[KMench]

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