High Phosphate, Low Nitrate

[mossanimal]

What are the most common reasons for having high phosphates (0.25ppm according to Salifert) and low (0 according to API) nitrates?

I will say right now that I have very actively growing Chaeto, a separate mangrove refugium with deep mud and the styrofoam sheet keeping the mangrove propagules upright works as an amazing algal scrubber. I also have only 3 fish in my 90 gallon tank. In addition to flake and pellets I also feed a homemade frozen food composed of fish, scallops and nori. I do rinse that well before chopping and freezing. But maybe that is the issue?

 

[rhitee93]

I'm interested to see what people say because I'm in a similar situation. I have to dose nitrates to keep them above 0, but my phosphates are slowly climbing.

I've heard people blame the source water for phosphates. What are you using for salt/ATO water?