If you send me 18$ I'll send you a 2 GOOD sponge filters (same as the one's you'll find in blkwolfe's large tanks). Or you can find some on aquabid etc (in quantities of 8-10).
Yes remove all fish that aren't discus, it's bad enough you're getting discus from many difference sources and plopping them in without proper quarantine, you don't need to make things worse by keeping other fish of questionable source in there. As a newbie with discus - you should have nothing other than discus in the tank.
If you're using a plain paper towel (nothing printed on them etc) then they're fine to use in tank. Generally they are just paper, and anything that may leech will be massively diluted by the water as you refill.
If they're not eating what you put in the tank - then there's a problem, they should be relatively aggressive feeders. They may wait for the food to fall from the surface to 'eye level', but then the feeding should start. If it doesn't you have a bigger problem that needs to be investigated and solved. 30 minutes of the food spoiling in the tank isn't a good thing, remember that old "as much as can be consumed in 5 minutes" that's printed on just about every can of food and parroted on every website/FAQ?. Start with a pinch of flake, if they eat it then add a little bit of something more substantial (bh / blood or black worms).
That picture of the tank bottom basically covered in bloodworms says a lot about your care. I don't think I'd feed a dozen discus that much food in one sitting - that's more than mine would eat in a day (And my 6 are much bigger/fatter than yours).
Andy
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