For an aquaclear 20, I got biomedia included. If I add another aquaclear 20 bio media in it, then would it be like an additional aquaclear 20 to make 2 of them? Or, instead of 2x the filter, would it be like 20% more filter power or what?
Under ideal conditions, doubling surface area such as, say, adding another same-size foam, has an additive effect on filtration, to a limit. Say double the foam gets roughly double the filtration capacity, so long as flow rate and turnover rate is maintained. However you must realise that the filtration capacity will only ever meet current bioload, so with regards to adding new fish, this must be done slowly to allow bacteria to grow to the current increased bioload.
I have to ask how you know the sponges don't give you beneficial bacteria like the bio max. Are you doing electron microscope scans of your sponges checking on bacterial colonies?
Swiss Tropicals recommends slapping the larger foam blocks on the driveway to loosen the muck trapped inside. Obviously the same basic principle being applied.Try slapping the AC110's foam sponge block against the side of the bucket.