Clean Up Crew, they consist of snails, hermit crabs, crabs, shrimp etc. They help with algae control and eat excess food the fish didn't consume and fish waste. Are you running a skimmer, this also helps with controlling nitrates by removing excess nutrients/proteins from the water? Are u using tap water for PWC
's or RO
water? Did you test your the Nitrate level of your tap water? these are some of things to check and that will help you out. Oh yeah what type of filtration are you using and has it been cleaned out?