Nitrates ~0 ppm while Phosphate ~0.25 ppm what to do

WallysWorld · Nov 15, 2018

For almost a month nitrates have been at the low detection limit of my test kit. Phosphorus has been steadily increasing from 0.11 ppm to currently 0.25 ppm. I haven't had a ton of algae in my tank. I do have a small amount of bryopsis, and I'm a week into treatment with Reef Flux. My tank is small Red Sea Reefer 170 (40 gallons total water volume).

I use RedSea Nitrate Pro for nitrate, and Hanna ULR phosphorus test kits. I also did a Triton mail-in test, and results closely aligned with what I measured at home. I trust my testing.

I dose NoPox daily with a dosing pump, 2.5 ml/day. Should I be doing something else?

Nburg's Reef · Nov 15, 2018

If you add nitrates (sodium nitrate or potassium nitrate) you can effectively reduce phosphates because it will allow coral and algae to start growing and using up phosphate. Coral and algae need both to grow, so if you limit nitrates they won't use up the phosphate in the tank, which can then climb. They use a lot more nitrate than phosphate, so if both are equal, nitrates will reach 0, while phosphates will build up. However, this could cause a lot of algae by just adding nitrates.

If it were me, i would do 2 things: slowly dose nitrate and slowly introduce phosphate reducer like GFO. Slow is key because any major swing in either way can affect corals. I would done nitrate to raise your nitrate to about 2 ppm, and depending on what you have in your tank, you might be surprise to see that drop to 0 ppm the next day. Adding GFO, start with 1/4 to 1/2 the recommended dose then slowly increase over a few weeks.

EDIT: just saw you use NoPox. I don't have experience with NoPox so that may work too, but my experience with GFO has been good.

Also double check to make sure you are not adding anything, like low quality food or too much frozen that might have high phosphate content.