Right, if the tank is that cloudy then check your water readings. Post your ammonia, nitrite, nitrate, PH, SG, and temp. Pre-mix your water for at least 24-48 hours. If the PH, SG, and temp match your display EXACTLY then you can do 50% changes. Don't add all of the water right back in. Add some, then let wait for a bit, then add more. Watch your equipment. Don't let anything run dry or the heating element of the heater to be out of water. BTW, Welcome to the boards!! How long has this tank been set up?