If you are going to have two sponges, both will need rinsing eventually as they will clog up. Id alternate cleaning both, so sponge 1 one week then the other a few weeks later (or whenever it starts to get clogged, could go longer or shorter between rinses depending on your stock). In other words, stick to a cleaning routine that works for your tank. Always use aquarium water though, and dont rinse the life out of them trying to get them to look like new - a few quick squeezes into a bucket will be fine to remove the bulk of the waste from them.lunanightlock said:I'm going to have two sponge filters in my tank. I was wondering since I have two, would it be ok to rinse one sponge in aquarium water (as needed) during water changes? That way not all of the beneficial bacteria would be rinsed away.