We have a 55 gallon tank, live substrate soil, live plants, rock, angel fish, tetras, glass catfish, pleco, otos, clown loach, canister filter from Eheim, all other chemistyr is great, nitrates, nitrites, oxygen, pH, etc. Except for phosphate. It's high. We tested tap water, barely any phosphates. We checked out the food we were feeding, nothing wrong there. We do regular water changes and soil vacuuming, etc. We tested our CO2 liquid ad it had high phosphates. So we found the culprit, but now we are having a hard time getting the po4 out. And we have staghorn algae to prove it. We are trying different filters in the canister filter...hoping for results soon. We planted more plants...try and beat out the algae. Any thoughts? This is a freshwater set up by the by.