Don't change the water and clean the filter at the same time; you are
re-starting the cycling process. Ideally only change half the filter media
at a time, so that some bio-bugs remain. Have seen the same thing happen
when I changed the water AND cleaned all the filter media; what happaned was
power got turned off to the canister filter for over 24 hours, so all bugs
probably dead, so had to kill off what's left, and changed some water to get
rid of N build-up in the tank.

Cheers,
Poe

"Victor M. Martinez" wrote in message
...

I've been meaning to post here about the cloudiness that sets on my large
tank after I make water changes and fertilize the plants. The small tank
doesn't get it, just the big one. Yesterday I changed about 30% of the
water and fertilized with Fluorish, Fluorish Iron, Fluorish Excel, plus I
added some Freshwater Trace. Like clockwork, the water started turning
cloudy about an hour after the water change. This morning it's cloudy, but
it should start clearing this afternoon. I also cleaned the filter
(Eheim), rinsing all the media in it.