Not if it's filthy or plugged up. Washing your sponge in aquarium water will remove detritus and 'stuff' that will make nitrates. The biological filter is in the interstices of the sponge and should not be affected. SH
I think that is good advice. I usually just do it every other time I change the water. Since I do water changes about 1/week, that comes out to about every other week for filter rinses. They are always full of nasty growth and gunk in mine.
I have 2 fluval ones for hospital tanks, i would invest in a fluval two as it will be better than the fluval one in that size tank.
As there is not much room in the fluval one to add floss, and carbon when you need it.