Hi all, is there any tips in washing the cotton wool in the filter in order not to destroy good bacteria? My filter have just 1 piece of wool, can I wash it with tap water? Or must I draw out some SW in the tank to wash it? How to wash it? Just dip a few times in the water or scrup it? What if the wool is in bad condition? I have to replace it with a new one, then how to save the bacteria?