Just my 2 cents. How I understand it is, you bb gets killed by a contaminate, or you add a large amount of bio media, so your bb releases and becomes kind of free floating. That's your white cloud. It's not toxic to your fish, but usually the reasons for it happening are. I've had the best results from not touching anything so long as your levels and nitrate aren't in the red zone. It will cloud, stay clouded awhile ( I had it stay clouded when I upgraded a tank to double it's size and added a bunch of ceramic rings the bb had to colonize for a couple weeks), and then pretty much clear out over night once the bb starts clinging back to solid objects. Basicly you want to avoid disturbing the gravel, filter media, and cut out the feedings since they'll add nutrients into the water. I was also told to avoid water changes until a little while after it clears, then just do a "pure water" change not vaccuming etc. Then get back on schedule. Same reason you only gravel vac half the tank at a time, change filter media staggered etc. Glad everything's back on track, and good luck with yours paul - N
(if I'm understanding this wrong do speak up as I'm totally trial and error taught)