reef man,
when they spawn again (in 2-3 weeks with good feeding), DO NOT clean the sponge filter.
sponge filters are great for fry tanks, as they support a micro-biological community that is an excellent food source for newly hatched fry.
when you do clean your sponge filters, all you should do is squeeze them a few times in a bucket of water from the same aquarium. this will unclog the filter,yet permit enough of the good bacteria to remain and repopulate the filter.
reef man, i am so glad you didn't ask about reef tanks.
set,
opinari