Foam filters? Do you mean sponge filters?
Do they look like this?
It's an air driven filter - and is supposed to be very good for biological filtration and some mechanical filtration. I "think"
they work by the air displacing the water and that causes a vaccume in that tube thing that forces water through the sponge? Alot of people use them with fish fry and they do not have the strong current produced by power filters.
The foam I was talking about is this:
it is made for the Aqua clear filters, but I use it in my aqueon filters in place of the cartridges. I stuff in inside my filters. Most places will say to replace then cartridge after a month BUT then you are also throwing out all the bacteria you WANT to keep. You can either swish the cartridge in old tank water when you do a water change to wash away the junk but after a few months, the filter floss (which is what the cartrdges are made of) tends to fall apart. However, the Aquaclear foam will last for a LONG time. it will do both mechanical and biloigical filtration but not chemical (which is what the carbon in the cartridges is for). In My opinion, you don't really need chemical filtration unless you are trying to remove medication rom the water or the water has an odor. Carbon only lasts for about a month so it's a bit pricy after a while. I only use carbon reguarly in a tank with alot of snails because the water gets smelly in like a day if I don't.
I have my girls in a 20 gallon but started them out in a 10G.