i have to say i havent....my tank has been pristine for over a year last month i noticed a few problems.....slime algea started forming, flatworms out of control (my rockks are orange) i have been sucking them up every other day or so so i can get to a managable level to use flat worm exit. i am currently cleaning everything a little everyday hope to have a 50 gallon water change and all pumps cleaned of by friday. the exzena has been growing for about 6 months. i will check my water tomorrow.