Are there any freshwater organisms that will eat fish waste?

Answer 1

Not really. You should have a few catfish in your tank, depending on the size of your tank. They will take care of any excess food that you feed. Have a good bio filter & an underwater filter to work best. You should also have a cleaner gadget that sucks out the water. Every so often you should stir up the bottom gravel until all the dirt & waste is floating is up out of the gravel (no need to take out your fish, leave them in), then use your suction cleaner, put the suction end in the bottom 3 inches of water, not in the gravel, to suck out the bottom dirty water down about 1/4 to 1/3 of your total water, no more than that or will shock the fish. Refill with room temperature water that has been left to set for about 12 hours before hand or just use a dechlorinator to get any chlorine out. When you let your new water set for awhile the chlorine gasses will escape out. This all you need to do to keep your tank clean. Do not overfeed your fish. More tanks get dirty by over feeding and that is not healthy for your fish. Also leave the algae that is growing on the sides of the glass on the back wall of the tank. Algae growing in a tank, shows a healthy tank and you want to leave some of that algae in. Purchase a Chinese Algae eater, hardier than most of the algae eaters to help keep down the growth naturally.

To be more specific, there are bacteria that do indeed break down the waste, producing their own waste which may or may not be more beneficial to the ecology of the tank. Aquatic plants, on the other hand, will make use of the nutrients that fish waste releases. However, only in a heavily planted tank will they make enough of a difference to cut down on the need for vacuuming gravel and it takes more work (and much more expense) to keep a heavily planted tank than to simply vacuum the gravel on a regular basis.