High nitrates and very low phosphate

nicodoctor · Sep 4, 2020

I have a problem with my nitrate rate, with very high nitrates near 50 ppm and 0 phosphate with my hanna checker. I try decrease nitrates with water changes, using biopellets reactor and porous media... but I can’t. It´s thrue that I need to elevate my phosphate level in order to decrease together with nitrate later? I’m using frozen, but I have seen P suplements. Are they neccesary? Thank you

Vivid Creative Aquatics · Sep 4, 2020

nicodoctor said:
I have a problem with my nitrate rate, with very high nitrates near 50 ppm and 0 phosphate with my hanna checker. I try decrease nitrates with water changes, using biopellets reactor and porous media... but I can’t. It´s thrue that I need to elevate my phosphate level in order to decrease together with nitrate later? I’m using frozen, but I have seen P suplements. Are they neccesary? Thank you

Sounds like it got out of balance, and the pellets (or at least the bacteria that live on the pellets) are not working the way you need them too. I ran biopellets for a good 5 or 6 years and had this happen once, and had it go the other way another time (high PO4, no detectiable NO3)

in both cases, i was able to correct it by dosing the one that was low. Its been a while, so i don't remember the exact brands of the stuff i dosed, but I do remember, I usually found them in the Freshwater isles at my local fish stores.

If you decide to dose, you'll definitely want to monitor it and test on a very regular basis to dial in the proper dose of PO4 as you bring it up. As it comes up, you should expect to see the NO3 go down

1ByLand2BySea · Sep 4, 2020

Nutrient reducing bacteria need phosphate as well to be able to reproduce and multiply.
The best is to start dosing a Phosphate supplement. Zero phosphate in a long term is not a good thing for any reef tank inhabitants.
Tryin to raise the PO4 with food will also raise the NO3 as well so there is a benefit in dosing with a phosphate supplement.

Nano sapiens · Sep 4, 2020

Yes, denitrifying bacteria require some phosphate to be present to process nitrate. However, if you feed your aquarium regularly you should have some phosphate cycling through the system, even if you can't detect it with a phosphate test kit. May, or may not, be enough for the denitrifying bacteria to hold a lower NO3 level depending on your system.

I had the same situation a while back. NO3 was up over 50 ppm, while PO4 was undetectable (Red Sea Pro Algae Management kit). I removed some excess fish to lower the bioload, lowered the amount of food (just enough to keep the fish properly fed), cut back on pellets and ReefRoid feeding of the corals and regularly removed detritus with the water changes.

Currently I have NO3 consistently reading 8-10 ppm (not bad), but am working towards ~5 ppm using low-level vinegar carbon dosing ('low-level' since I don't have much excess PO4 in the system to support a much enlarged bacterial population).

It is possible to tackle high NO3 without adding PO4 supplementation (when PO4 very low or undetectable in a system), just takes a bit longer and requires a multi-prong approach. I enjoy these kind of challenges, but understand that many reefers want to fix a problem like this as quickly as possible.

If you do add a PO4 supplement, just be careful not to over do it and test often to confirm.

Tdoan · Oct 23, 2020

I am having the same issue but my PO4 is .07. I am not using Bio reactor. My nitrates are around 46. I am currently doing big water changes but it doesn’t seem to move it much. I am using a Hanna for both test.

Klyph · Oct 24, 2020

Tdoan said:
I am having the same issue but my PO4 is .07. I am not using Bio reactor. My nitrates are around 46. I am currently doing big water changes but it doesn’t seem to move it much. I am using a Hanna for both test.

What would be a good supplement to raise phosphate from 0.00 to 0.03?

jsbzcmcdaniel · Oct 24, 2020

I'm a big fan of making my own phos and nitrate dosing mix. Its far cheaper and it's more potent than commercial brands. I used Loud Wolf to dose both. TriSodium Phosphate and Sodium Nitrate.