High nitrate low phosphate

Randy Holmes-Farley · Mar 4, 2023

jda said:
If you ever dosed any algaecide like Vibrant, AlgaeFix, etc. then people are struggling to keep chaeto even long while after not dosing anymore.

I have seen too many tanks, including some of my own, with macro struggling in the 25-50 ppm of no3 range and then full out struggle over 50ppm. The proverbial "I have 100 nitrate and no algae" type of deal. po4 plays into this too.

Carbon dosing is a long term, daily thing. Go slow, keep at up and slowly raise the dosage. Your skimmer cup should be the first thing to watch. The skim mate should change, smell totally foul and rancid with hugely increased production. When all of this starts to happen, freeze the dosage. Don't keep raising it. It will do the work over time. There are many articles on this that you can read. I used just plain old sugar in a FOWLR with good success and after I got the nitrate down to about 20-25 some GHA started to come back... then I got it down to like 1-5 ppm and the coralline started to take over again. Vinegar, vodka, sugar and ethanol all have supporters and also detractors, but in the end, they all work. Growing bacteria with organic carbon does not appear to use orthophosphate, which is the only kind that we can test for. It has to use other kinds or else organic tissue cannot form, so pay close attention to your corals, if you have any, since they likely use these other kinds too. Just remember that high tide lifts all ships, so other types of things will grow more too.

I’m not sure I see evidence that bacteria driven by organic carbon dosing cannot use orthophosphate, and I’d be surprised if it is true. It is true that such dosing drops nitrate a lot more, but that can be explained by a Redfield ratio of uptake coupled with some release from rock and sand buffering the downward drop.

On the chaeto and nitrate, I don’t see much evidence of folks finding it harder to grow chaeto at high than low nitrate. It can be an issue at any level for other reasons.

mike550 · Mar 4, 2023

@jakem42 I have a 120 and had a similar issue as yours but nitrates werent quite as high. But like you I couldn’t do massive water changes. So I ended up doing 25G water changes each day for a few days to brinf the nitrate level down quickly then started using NoPox. Worked well but I would caution that I started with 25% of recommended NoPox dosage to make the change gradually.

jakem42 · Mar 4, 2023

Dan_P said:
How long did you try dosing? what your maximum dose? How fast was the Cheato growing?

Chaeto wasn’t growing at all. I dosed for about 3 weeks

jakem42 · Mar 4, 2023

mike550 said:
@jakem42 I have a 120 and had a similar issue as yours but nitrates werent quite as high. But like you I couldn’t do massive water changes. So I ended up doing 25G water changes each day for a few days to brinf the nitrate level down quickly then started using NoPox. Worked well but I would caution that I started with 25% of recommended NoPox dosage to make the change gradually.

I was using nopox daily for 3 weeks at the daily recommended rate and saw no change in nitrates at all after 3 weeks. I unfortunately can’t get away with 25G daily I could probably do that weekly

gbroadbridge · Mar 4, 2023

jakem42 said:
I was using nopox daily for 3 weeks at the daily recommended rate and saw no change in nitrates at all after 3 weeks. I unfortunately can’t get away with 25G daily I could probably do that weekly

Keep going with the Nopox or just plain vinegar .

It can take several months to start working.

You don't want things to happen fast anyway.