Tarpon and bud, yes there is a charcoal filter and a bio-wheel. This tank has not gone through even one water change because it cycled pretty quickly, I think. My hope is that the wheel got enough BB to compensate for the removal of the sponge filter after the fish have been in there for a couple of weeks.--?? I'm worried that just the big water change will throw it off. Of course, I will rinse the carbon pad in old tank water.
I can put the sponge in a bucket with its tubing and feed it, no problem. I could get it really, reallllly dirty in the bucket by throwing in some goldfish flakes or maybe a shrimp!
I'm feeling another experiment coming on--albeit a stinky one!
The only reason, no two reasons, I want to take it out is because this is only a 5g tank; the sponge is fairly large for it, and I want to give the Endlers more space, and I'm hoping to not have to buy another active sponge filter for my next tank. It's not that I'm all that cheap, but I've grown kind of attached to the thing since it worked wonders for me--well, that and all the smart and helpful people in here!