Bryopsis, Kent Tech M and carbon?

[Randy Holmes-Farley]

Just wanted to through this out there... My brother is chemist of sorts, and he offered to test my water using some sort of plasma microscope....I asked him what my copper in my tank was at and he said it was 3 parts per trillion....

I should mention that at the time of the water sample collection, I had been dosing my bryopsis filled tank with Tech M for about 1 week and I had brought my levels from 1350 to 1800.... So I had added a significant amount of Tech M....

Doesnt sound like a lot of Copper.....

Unfortunately, I don't think that is likely accurate. More likely it is 3 parts per billion, or maybe some unrelated higher number (which is above NSW which is 0.4 ppb or 400 ppt). As I understand from measurements I've seen, tanks accumulat copper and likely do not start lower than natural levels. My tank when I measured it (using Inductively Coupled Plasma-atomic emission spectroscopy) was closer to 13 ppb, despite the fact that the IO that I used was lower than that.

 

[Randy Holmes-Farley]

I accept that this is all theory, because I/We have no way of testing to illustrate the model....but it makes interesting reading

Perhaps, but it is well known that in the ocean, nitrogen and phosphorus and iron are generally the limiting factors (aside from space, light, etc).

Cations like magnesium and potassium are in huge abundance in seawater, even if they may be limiting in soils or fresh water.

I also do not see any substantial relationship between magnesium and phosphorus in Figure 5 bottom panel. As long as there is some minimal magnesium (far, far less than in seawater), the plants grow relatively independent of it. Only the lowest magnesium test (at 2.4 uM = 0.06 ppm magnesium) is the magnesium noticeably limiting.

In fact, the author states:

"No uniform pattern was observed in the P X Mg experiment. Liebig responses were observed at magnesium levels 1 and 2, whereas magnesium levels 3, 4, and 5 were classified as undefined."

The reason we focus so much on nitrate and phosphate is that most tanks (at least those without very aggressive export) have N and P in far higher concentrations than seawater, so trying to bring them back to natural levels is the most appealing way to limit growth (aside from, perhaps, herbivores).

 

[Heliman]

Yes Randy...nothing I could disagree with in your response.

But based on reading literally hundreds of posts where reefers have put mountains of effort (and money) into the reduction/elimination of phosphates, it is always a puzzle why these explosive algal blooms happen to some reefs and not others. I have often wondered what was the differential.

I theorise that at the levels of phosphate minimisation we can get to with GFO, husbandry, water changes etc, how come the algal blooms still occur, surely they would be in someway nutrient limited at this stage and under Liebig (or MLH) theory, growth would be hampered, if not stopped.

Or is it that at the levels we can get to (or more accurately, test for) we do not approach a growth limiting nutritional environment ?

But if, repet if, the Phosphate levels we achieved were growth limiting, then Magnesium would enter the equation ?...or not ?

For my own elucidation, I have a sense that Nitrate may be the bigger nutritional nuisance and one which takes the bigger job to minimise.

After all, what do we actively do to manage nitrates in the same rigorous way that we do phosphates......water changes ? physical removal of algae ? herbivors ? What would be the level of nitrates that we could consider to be nutrient limiting ?

My next move is to do whatever I can to adopt a more rigorous nitrate reduction programme , whilst maintaining my normal phosphate controls via GFO and bio-pellet dosing....see if this has any different effect on algal propogation.

 

[tmz]

That was interesting. Thanks for sharing it.

Regarding nitrates and magnesium and P limitations here are few thoughts:

Nitrates are rigorously managed by many reef keepers via denitrators of various types and numerous other tactics . For the last 5 years or so they nitrate control is more commonly achieved by organic carbon dosing and consequent denitirfying faculatative heterotrophic bacteria growth which also use some inorganic phospahte.
Primarily the push against nitrates is focused more on coral health than algae growth; as excessive nitrogen is thought to drive excessive zooxanthelae growth along with excessive oxygen production and a transformation of the symbiotic coral /zooxanthelae releationship to more of a pathogenic one. I do not know the limiting levels for N for nuisance algaes but surface reef waters hold about .2ppm or less.
Further many cyono bacterial strains another common pest can produce fixed nitrogen leaving phosphate as a primary target for limitation.

This notation in the paper was interesting to me :

"..In particular, we predict that plant responses to nitrogen availability
will follow the MLH model, whereas Liebig’s law is
the prevailing model describing plant responses to the other
nutrients"

That suggests to me P reduction would be effectively limiting independent of other costs and benefits of the other elements used in the study ie,
N,Mg, K

 

[Heliman]

TMZ

That is the point I was attempting to make.....

We saw for quite some years, beginning with bio-balls and ending with complex sulphur/chemical methodology several methods to get vigorous with nitrate control to achieve nitrate minima in our reef tanks. I agree that lately, the technology of carbon dosing via Vinegar/Alcohol and more recently the use of bio-pellets is advancing this methodology. Along with the fact that so many reefers rely on Chaeto/fuge live rock and substrate to do the same thing.

I dont know if many reefers have been able to manage nitrates down to the 0.2 ppm that you mention as the benchmark for NSW...I certainly have not anyway :facepalm:

That is why I still wonder whether nitrate is indeed the big bogeyman.....

And if we again visit the research in question, do we not see that the target of a Liebig response would be more effective than that of a Multiple Limitation Model ?...Fig 1, P 144 seems to suggest that the most desirable outcome for us in respect of nutritional deprivation goes is to get the plant to respond in a Liebig way, not a MLH way...

Hence my thoughts on nitrates "maybe" being the dominant concern.

All good stuff !!!....I think there is a breakthrough needed/coming in the management of nuisance algaes...but I dont know from where...I hope some bigger minds than mine are working on it, it would remove one of the biggest factors that kills the hobby for newbies.

 

[tmz]

Many have reported nitrates at or below the <0.2ppm level at least according to what hobby grade test kits can tell us. I have, first with a sulfur denitrator,sand beds and refugia and for the last 3.5 years via organic carbon dosing(vodka and vinegar) along with cryptic and chaetomorpha refugia as well as skimming and granulated activated carbon.
Unfortunately, it seems with some methods targeting 0 nitrogen, deficiencies actually seem to be causing coral problems requiring dosing amino acids or extra feeding to source extra nitrogen.

 

[Randy Holmes-Farley]

Yes Randy...nothing I could disagree with in your response.

But based on reading literally hundreds of posts where reefers have put mountains of effort (and money) into the reduction/elimination of phosphates, it is always a puzzle why these explosive algal blooms happen to some reefs and not others. I have often wondered what was the differential.

But if, repet if, the Phosphate levels we achieved were growth limiting, then Magnesium would enter the equation ?...or not ?
.

Not (IMO). Algae cannot "use" magnesium in any way that replaces phosphate. The paper doesn't show any, and there is no chemical reason to think it remotely possible, as they are never substitutable for each other in any molecule.

I do not doubt other chemicals can be limiting in reefs. There are lots of trace elements that algae need and may get depleted in reefs. I just do not think it is necessarily a good idea to make them limiting because they may become limiting for many other creatures as well, such as corals.

FWIW, I do not think there are any hobby test kits available for nitrate and phosphate that allow folks to confirm readily that these nutrients are at natural levels. Consequently, folks saying they has 0 nitrate or phosphate may still have quite a bit more than the ocean. Much of it may also be found locally if the algae is growing on phosphate bound to rocks and sand, or on a pile of decaying detritus.

Likewise, since we cannot easily measure these levels, we also run the risk of possibly driving them too low, and that is something folks using aggressive measures should keep in mind.

 

[bertoni]

I agree that we would need far more precise and accurate measurement equipment to determine whether our tanks are phosphate or nitrate limited, for example. Unfortunately, the equipment would be rather costly with current technology.