you overdosed and caused an issue. did you test your phosphate level, and dose correctly per directions? waterchange, activated carbon, and time it will go away. do not dose anymore until you get it right or things may die. if you dont have an accurate phosphate (like hanna) kit do not use. its 1ml per 4gallons to reduce phosphates by 1ppm. if you have good ro/di water, good waterchange schedule and dont overfeed you shouldnt need to dose that.