Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
It is OK to clean the filter. Done right, it does not cause a mini-cycle.
When I set up a tank, or make a mess, I make sure the filter has some floss in it, and run it. I check it the next day, and rinse out the floss, then let it go. Usually the first 24 hours of cloudy water is when the maximum amount of fines get trapped by the floss.
Water changes are fine with respect to ferts.
If you are following the EI method or any other, there is no problem at all with an extra water change, if the tank needs it. I would just pull out enough water to rinse the filter media, though, unless the tank water still had not cleared in 24 hours (might still be a faint haze- that is OK). Even in the worst case scenario, where a tank needs a much larger water change, or even a double water change, I still do not alter the fertilizer schedule- just keep on fertilizing per schedule.