Could the cloudiness be due to CO2 reacting with limewater to form CaCO3. I too had this problem. My CO2 setup is a DIY bottle of yeast and sugar solution placed directly in the tank. I noticed that when CO2 concentartion is at peak (ie i turn off aeration), it becomes cloudy. When aeration is turned on, water becomes crystal clear. Where did the source of limewater comes from. Stones, clay? I'm not sure.