we have no chlorine in our water, so I rinse them in the sink, but yes, you are suposed to rinse them with tank water. I use 2 sponges in my ac110 and that is the only filter on my 55 atm and it provides enough bio-filtration as well for that tank (though it is undestocked right now). It provides GREAT mech. filtration, and on our other tank I have an ac70 with 2 sponges and an emperor 400 for bio. Both ac's seem to do great with 2 sponges, and are the best for mech. IMO.