Hi metfan581
You have been given excellent advice by the others, so I won't repeat it, but I want to add something about cory cats.
Corys are great little fish to have, but don't get them if you are only looking for a fish to eat leftovers and not because you really like them. They have their own needs and feeding requirements like all the other fish do.
One of the things corys especially need to thrive is lots of fresh and clean water, and a very clean bottom. If leftover food accumulates, harmful bacteria grows on it, and the first ones that will become sick from this are the corys.
Feed less, even if it means you are doing very tiny feedings. If necessary you can feed your fish twice a day if you don't think they are getting enough, but you will probably find that they don't need any where near as much food as you think they do.
As for the filter cartridge, you can keep cleaning it in used tank water until it literally falls apart. Don't worry about what it looks like. The bacteria will do better the older it is, and that's what matters.
