Redfield Ratio - significant factor in reef tanks?

[coralcruze]

excellent thread...
tagging along

 

[Coralsea_co]

Hello to all,excellent thread....
Redfield Calculator :
http://www.aquariumhobby.nl/zoetwater/calculators/redfielduitslag.html

 

[JDowns]

I read a paper a while back that showed the ratio of N to P was much lower in coastal reefs than the Redfield ratio. It also attributed P deficiency as a promoter of coral bleaching in Euphyllia.

 

[JDowns]

Since its always good form to post a link to a paper when referencing a paper.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5441187/

 

[LadyTang2]

Randy, are you at all implying that NO3 and PO4 may not be necessary for coral health? I don't think you're implying that, and there must be a certain amount of NO3 and PO4 that is needed in the water column for coral (and/or their symbiotic xoozanthellae) health, or do you think (or know) that corals utilize there nutrients from a source other than the water column?



Yes! I've tried explaining this to people before and their eyes gloss over. Once you realize N does not equal NO3, and P does not equal PO4, then add to that not knowing if the particular ratio is using weight or atomic weight it gets pretty complicated for the average Joe Reefer!

Is what you are saying here that since N and P exist in more forms than what we test for (which is no3 and po4 right?) that the number we use to see if we are close to the redfield ratio are inaccurate? Did I get that right?

If that is right, then it might be useful to know, which (N or P) has more other forms not being picked up by our tests. In other words which to assume is actually higher, and which to assume if lower usually?

 

[Randy Holmes-Farley Verified Community Expert]

Is what you are saying here that since N and P exist in more forms than what we test for (which is no3 and po4 right?) that the number we use to see if we are close to the redfield ratio are inaccurate? Did I get that right?

If that is right, then it might be useful to know, which (N or P) has more other forms not being picked up by our tests. In other words which to assume is actually higher, and which to assume if lower usually?

There are sources of N and P that we do not measure routinely, but that is not why I think ratios are not the best way to think about nutrients.

Here's a blurb from a similar thread a couple of days ago:

I am not a fan of ratios as target levels. If both are independently targeted to proper levels, there is no need to think about ratios.

I don’t deny that off optimal values may cause different types or extents of problems depending on the other, so a ratio has importance, but not as a target.