Nutrients/ alk ?

[lars]

I know that when you run a low nutrient system you have to also have low alk. My question is are we talking 0 phos and 0 nitrate or would 0-2 nitrate and .02 phos be considered low nutrient? The reason I'm asking is because I use to keep my alk at 7- 7.3 with almost 0 nitrate and around .04 phosphate and everything was good. I recently started trying to bring up my nitrates a bit and by doing so my phos dropped to around .015. It's now sitting at n- 3 and p- 2 and alk at 7.7. I've since lost a bunch of sps and the others look like there holding on. The rest of the tank looks great. I was assuming my issue was dropping the phos to fast and that's what burnt my sps. This morning however I was wondering if the problem isn't actually the p dropping too fast but more of having too high of an alk for my nutrient levels. I know it's not really an ulns but could this have been an issue? Rather then lower my alk I've been trying to keep my n at 2-3. It seems some of my other tank inhabitants appreciate the added food. I know only time will tell with the sps because nothing but death happens quickly in reef aquria so I figured I get some feedback on it.

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, this issue only seems to apply to SPS, not seemingly to any other corals. Probably because no others can grow skeletons as fast when alkalinity is elevated. Folks should not assume that this is a general rule.

That said, opinions likely vary on the exact amounts needed, but 2 ppm nitrate and 0.02 ppm phosphate is unlikely to suffer burnt tips , which is the problem with high alk/low nutrients. 1 ppm nitrate and 0.01 ppm phosphate may also be OK. Dropping below that makes issues more likely. What else you feed also has a big impact.

That said, corals may thrive better at higher nutrient levels than very low values, regardless of what the alkalinity is, but so can pests such as algae and cyano. The tricky balancing act is one that many reefers find frustrating.

 

[lars]

Thanks for the reply. I'm just gonna try and be patient and ride it out and try to just keep things stable.