Is the cloudiness green or grey? Green means algae, grey means bacteria. if it is bacteria you will need to be careful not to overfeed and really keep up on the water changes. You might also want to increase the biofiltration on that heavily loades tank. You can do that cheaply by adding a UGF rated for a 20-30G tank and powering it with your airstones. This will turn about 2/3s of you substrate into biomedia and not only reduce the available nutrients for the bacteria but also pull much of them out of the water column into the filterbed where they will work for you instead of against you.[/QUOTE

Algal blooms can be detrimental, but are pretty easy to reverse if caught early enough. Lots of water changes, adjustments in lighting (sometimes turning it off earlier each day by a couple hours), and good cleanings usually help reduce it immediatly, without the use of chemicals. Bacterial blooms however can proove much worse, and harder to get rid of. I suggest following guppy's advice for that if your "cloudiness" is more opaque rather than green. Like guppy said, up your filtration, and change it out regularly to ensure you are discarding the "yuck". If it is getting worse, or any of your fish have started acting stressed, removing them to a holding tank is probably your best bet for survival while you tackle this bloom. good luck.
--EMI