Zero nitrate - High Phosphate

[Uncle99]

Assuming I had a misread…. Tested twice tonight with near similar results. Still high but not nearly as concerning

So nitrate fine, maybe run some GFO to half the phosphate.
I’ve used Rowaphos in a mess bag successfully many times.

 

[manaman]

Some species of lyngbya can consume NO3 at a rapid rate and will not metabolize PO4. They often present as visually similar to detritus underneath rocks and lower light surfaces, many reefers often don't account for this organism and are left scratching their head at wacky test results. I'm not saying that's the case in this situation, it is a possibility however that the majority of people wouldn't consider.

 

[Randy Holmes-Farley]

Some species of lyngbya can consume NO3 at a rapid rate and will not metabolize PO4. They often present as visually similar to detritus underneath rocks and lower light surfaces, many reefers often don't account for this organism and are left scratching their head at wacky test results. I'm not saying that's the case in this situation, it is a possibility however that the majority of people wouldn't consider.

What is the basis for any cyanobacteria not being able to use phosphate?

https://www.sciencedirect.com/science/article/abs/pii/S164235930770188X

Mass occurrence and toxicity of the cyanobacterium Lyngbya majuscula under phosphorus-limited conditions in the Red Sea

"In addition, the study revealed that the growth of L. majuscula increased by increasing inorganic and organic phosphate concentrations. "