Nitrate

[DavidA]

So, a common subject, still needed to discuss as its something that surround the coral 24/7 and of our concern.
We had a thread recently where I posted an article about the negative metabolic effects of hign temp and high (0.19 so not ao high) nitrate together, and also the opposite beneficial effect of ammonium.
The discussion is relevent, is nitrate a problem also in normal temp or just when coral is getting stressed?

Since decades we have struggled getting nitrate down and invented nitrate reactors, carbon source method (vodka method) etc. We see nitrate as a pollutant, as its a waste product of the nitrification and insufficiently denitrification. Denitrification is always more hard to get a good turnover as it need anareobic areas which is harder to get than aerobic surfaces ofcourse.

So I think most aquarist agree we do not ignore a raising nitrate. But, where is the limit and how much concern should it make? We have a lot of examples of tanks that look fine with high nitrate. That can be because of adaptation, some corals have died so you now have a selection , and some corals genetically are less sensitive to nitrate .

I found another study(they are refereing to the previous one), with a different design from the other we have discussed, where they have compared a corals metabolic response in high temp (30 gr) versus normal (26 gr) with and without increased nitrate, AND also compared to ONLY high temp.

The interesting finding in this study is:The coral did NOT respond badly to solely high temp 30, but when you added nitrate(0.56 ppm NO3) to that it responded badly: reduced photosynthesis efficiency, increased risk of thermal bleaching, and decreased bacterial diversity. This was already at nitrate levels we consider low. With even lower nitrate (0.15 mg/l) similar findings but not so severe. (That resembles the study from 2021). Note also that the stress symptoms developed already after 2 days with a culmen day 14. There was no PO4 limitations.

In the era of zeovite, we discussed ultra low nutrition, and many with me was against that. I am still that. BUT what we didnt understand at that era was that it was probably the low PO4 that was the issue, not the low nitrate. Some of us dosed nitrate as we where scared. I think that was a great misunderstanding as we didnt know better.
Today, I am afraid of low PO4, and high nitrate.

My own tank: PO4 AND NO3 is raising last months, a lot of fishes. I will introduce one more deni-block, but so far do not open the GFO box as long as I am below 0.1 in PO4.

This field has really developed, and when people say its ok with 25 ppm in nitrate I just wonder if they have something more substantial than just "I have seen tanks with that and it looks good". Its a very weak argument, and I will say those choose to ignore these interesting data, even if its not 100% proven, its hard to deny these beatiful studies.

https://www.sciencedirect.com/science/article/abs/pii/S0141113625001552


Jonas

For those advocates of low nitrate, what do you consider an optimal nitrate level when running a chaeto reactor to lower phosphate? Won’t low nitrate levels suppress the capacity of the reactor to lower phosphate (low nitrate acting as the rate limiting step)?

 

[Lasse]

I have no access to the whole paper but the main point here is oxidative stress. I do not know the basic photosynthesis in the aquaria without elevated NO3. But if we assuming that some photosynthesis was taking place in low temperature/no addition, and high temperature/ no addition but was limited by bioavailable inorganic N—then I can have a well-functioning theory about what happened or is happening in high temperature(NO3 addition).

Some fact - photosynthesis results in oxygen production – initially as oxygen radicals, but diffuses out as molecular oxygen into the surrounding water. Its a diffusion which means that the rate of export is depended of the surrounding waters capability to take up the oxygen production. If this process is hindered - oxygen radicals will be build up in the tissues and surface of the coral - stressing and killing things it comes in contact with. By try and error - aquarist have already understand whats happens when you have a high photosynthesis by use a lot of water movement that present the microhabitats around the corals with water ready to take up oxygen from the coral.

I can´t see the construction of the test, circulation, lighting, amount of bioavailable inorganic N in control group, hence I can´t exclude that the result is due to bad circulation and the fact that 30 degree C water have around 0.5 mg/L less at 100% saturation compared with 26 degree 25 PSU saltwater

If you have the full article - send it to me by PM

Sincerely Lasse

 

[areefer01]

One of the challenges I see with these discussions in relationship to home aquaria is that when we lose a coral we do not always know why. Is it due to too low of a nutrient such as nitrate of phosphate? Is it due to them being two high? One being too high the other too low? Is it the ratio (trigger word) of the two? Traditional hobbyist are not able to do a post mortem necropsy examination or have that skillset.

Another note since we mention some displays with very high nutrient levels. Myself also being in that camp. We keep what grows and appears to be thriving. We do not continue to buy what we lose. Success is in what adapts.

 

[Gregg @ ADP]

In my experience, really low NO3 and PO4 has been more problematic than high NO3 and PO4.