50% water change and still 20ppm nitrates

[Milad]

now that i think about it
this problem is familar

When i first setup the tank, i had the same symptoms, algea growing fast on the glass

I added rowphos and it stopped

I removed rowaphos recently and it started

So maybe Im doing this wrong, I should start zeozyme and zeobac again so the bacteria can eat away at the phosphates?