I just recently set up a 125 freshwater tank...I have a 55 gallon now, but when i set it up a while ago i cant remember if this happend. Ok, water is in, treatments are in, filter and heaters are up and running, I added some sand from my established tank to this one to help the bacteria colony along, tank got cloudy for 1 day and is now crystal clear. I have the Mardel Live Ammonia reader hanging in the tank, which is showing 0.02 ammonia= caution. Now you are supposed to have ammonia during new tank setups correct? I have no live fish or plants in the tank at this time, just sand, and decorations. Its been a while so i cant remember if i had the same thing happen on my 55 gallon.