yup, Paul (Billaney) suggested that I do an Ammonia test and nitrates so i gave Animates a sample of my tank water and they came up negligible - so I bought some PH DOWN and did continuous WCs but the pH wouldn't come down so Paul suggested it was the gravel and I even took out ornaments that could leach - 3 days later all the fish were dead. The fish were all healthy and happy before addition to that tank and the pH was the only component that was different