I know this is mainly a reef forum (im on here for my reef tank) but my uncle has a fresh water tank (36 gallons) and his Nitrates are really high and wont go down. His ammonia and nitrites are fine, but nitrates are becoming an issue. Hes done multiple massive water changes, hes cleaned the substrate, and he only feeds the tank about once a week. Any idea what might be causing this problem? Thanks in advance.
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