I just recently bought a sponge about two weeks ago. I believe that the larger ones require a lot more attention than the hitchhikers do. The one that I have I feed oyster eggs and keep it out of the light. It seems to be doing fine, but then again its only been about two weeks. Sponges in general are filter feeders, and I think that the larger they get the more attention you have to give them in terms of feeding, which I target feed them every other day. While on the topic, the Dt oyester eggs that I got says to turn off the skimmer while feeding the tank, does this have to be done or do you think the skimmer can stay on?