clear fx pro has phosphate remover in it, and that could be your issue. i have to actually add gfo to my clear fx bag. i use the 450ml bag and my water volume is about 45 gallons. i feed 3 times a day and have a heavy bio load. it could be why i haven't seen any coral issues. perfect example off how different each tank is so different and how one thing works great for one but not for another.