Originally Posted by baron1282
I was always told not to squeeze the sponges. I normally would just take my hand and knock off the solid stuff.
This "advice" is often repeated. You will find that the sponge will be full of solid material and will take an extensive amount of squeezing to get it out. Usually the first few squeezes don't move much out, but once it starts to break up it comes more easily.
Try it your way and then try to give it some serious squeezing and see what comes out. The beneficial ( nitrifying ) bacteria is firmly attached to the sponge, and doesn't let go easily. Beneficial bacteria is aerobic and when a filter becomes plugged with solid material, the hetertrophic bacteria that consumes this competes for available oxygen with the nitrifying bacteria. If there is enough blockage, you will have areas in the sponge that become anaerobic, with neither type of bacteria alive.