Nitrates

[Pappy]

Randy,

First I would like to thank you for all the research and articles you have written over the years! I have been reefing for about 7 years and currently have a 120g full blown sps tank. I have always followed your recommendations on trying to mimic nsw levels and environment and have continued to have great success! I recently over the last 2 years have switched to zeovit and love it! The growth and color I get is outright uncanny!

I've seen this trend of high alk and high no3 being beneficial to sps and having a real hard time wrapping my head around it! I am under the impression that coral does not like no3. Why are there people suggesting things like high alk and high no3 could ever be beneficial to a reef tank. As if we know better that Mother Nature?! I've only one time had someone include a link backing this theory up but was unable to translate in English versus scientific jargon.

I am always looking to learn more and understand there will always be new and innovative ways of reefing but the above just doesn't make sense to me! Please explain to me why if it does make sense!

Thx for your wisdom and experience!

 

[Randy Holmes-Farley Verified Community Expert]

Thanks, Pappy.

Here's a section of one of my nitrate articles on how it boosts zoox, and that might help or hurt a coral, depending on the alkalinity. The bolded part relates to this issue.

https://www.reef2reef.com/blog/nitrate-in-the-reef-aquarium/

In addition to the concerns described above relating to the growth of potentially undesirable organisms that may be promoted by elevated nitrate (especially algae and dinoflagellates), corals can be impacted by nitrate. Many corals may not be bothered by elevated nitrate, or may even grow more rapidly with the readily available nitrogen. But in certain corals, especially those that calcify, there may be negative effects from elevated nitrate.

In most cases where nitrate levels have been examined in relation to the growth of calcareous corals, the effects have been reasonably small, but significant. Elevated nitrate has been shown to reduce the growth of Porites compressa (at less than 0.3-0.6 ppm nitrate),16,17 but the effect is eliminated if the alkalinity is elevated as well (to 4.5 meq/L). One explanation is that the elevated nitrate drives the growth of the zooxanthellae to such an extent that it actually competes with the host for inorganic carbon (which is used both in photosynthesis and in skeletal deposition). When the alkalinity is elevated, this competition no longer deprives the host of needed carbon.17

A second study on Porites porites and Montastrea annularis tends to support this hypothesis. They showed that elevated nitrate caused an increase in photosynthesis, in the density of zooxanthellae, and in their chlorophyll a and c2, and total protein, while skeletal growth decreased considerably.18 This effect may not always be true, however, since elevated nitrate does not appear to have decreased calcification in Acropora cervicornis (though the experiments were carried out under very different conditions).19

A third study, on Acropora pulchra, showed the increased nitrate increased zooxanthellae levels and the calcification rate.20 One other study 21, on Porites cylindrical, has reported that elevated nitrate (0.9 ppm) did not increase the rate of photosynthesis or zooxanthellae density, but actually decreased it, contrary to the other studies. They do not provide an explanation of why their results were different, though they indicated that the corals may have been expelling zooxanthellae, which would confound some of the results. Additionally, all of the corals in the study were stressed in that they lost significant biomass during the study compared to when first collected in the wild. Because of that effect, I do not put much faith in how this study may relate to aquaria where corals are growing rapidly.

Overall, it seems that elevated nitrate may spur zooxanthellae levels in corals, and aquarists may notice this as a darkening (browning) of the corals since zooxanthellae are golden brown. Whether there is a growth rate effect, and in what direction, may depend on the coral and the other conditions in the aquarium.

 

[Pappy]

Thank you very much! So additional questions I have are:

Do you think no3 effects overall color for the positive?

No3 more beneficial to have or not when referencing sps?

I have always believed that feeding sps at times is good and it's the food not the no3 itself effects the color. Is this accurate?