The brand name on Amazon is Misfans, Chinesium I guess. Pic attached. It has the round filters, one a sponge foam, one a charcoal. I've been reading extensively on using a water fountain without a filter so it doesn't get gross. I've removed those two to see if it helps, as they smelled up quickly. However they don't discuss the filter inside the pump cavity. It is not charcoal, looks like just foam, but already smells bad and has slime on the plastic around it. Is this filter essential to the fountain, or can I also try using the fountain without it? PS she isn't using it yet. I add a dental additive and a few drops of salmon oil to tempt her.