My API test always showed 0 detectable Phosphates. But had green film algea which led me to believe I had some phosphates. So I broke down and bought the Hanna checker PPB version. First test was more then the capabilities of the PPB checker. Tested again to confirm.. it was again higher then range for the checker. (Got worried) so I purchased the Hanna checker PPM and tested 1.2ppm.
Yikes!
But much to my surprise, tank looks great other then glass needs cleaned daily. Started GFO and went from 10% to 25% weekly water changed. It’s slowly coming down, but long story short: I don’t think your phosphates are ridiculously high.
Just my experience, but im No expert lol
77ppb to ppm= 0.236ppm.
here’s a chart I use to convert
https://www.hannainst.com/hubfs/006...phate-conversion-table--hanna-instruments.pdf
Hope this helps. Take care