sponge retrofit topfin 30

[macbrak]

I currently have a topfin 30 that I'm making do with. Yeah I've heard how much the topfin stuff sucks, but it came in a petsmart kit and was basically free after adding together components I needed so it will do until it gives me trouble.
I have added an aqua clear sponge in along with the filter media and carbon cartridge that comes with it. My logic is to have a bacteria buffer that isn't disturbed everytime I have to clean the cartidge. Is this an improvement or do you think the flow will be impeded so much to lose and benifit gained by extra space for bacteria to grow?
It is my thought to eventually dump the carbon altogether and use the cartridge as mechanical filtration.
Is there any major flaws in this plan that I'm overlooking?

[Sumpin'fishy]

Your plan sounds fine. Best you can hope for with that filter. I, too, started with a Top Fin filter!

[macbrak]

Thanks, I hope to move up to something else, but trying to do the best with what's at hand.