Feeding Goldfish

I have a 10 gal aquarium with 2 small goldfish. I was using a 10 gallon water filter. It is a 12.99 filter that hangs on the side of the tank. I had a losing battle with cloudy water and plus the filter would clog every two days. I would change about a gallon of water a day and could not keep up with the cloudy water. I decided to drain the tank and clean it. I put in two to three gallons of treated water in the tank. I still use a air stone but left out the water filter. I use no gravel, it is a bare bottom tank. Now I can see all the waste these two goldfish can produce. The waste is mostly short and white like, some are stringy like. I feed very little, once a day and I am still suprised how much waste is produced. The directions on the food containers seem excessive for me. I see very little about feeding in this newsgroup about feeding. The question is : how little can I feed two small goldfishes(about 1 1/2 inches) without starving them to death ? Right now I am vacuming once a day and removing and replacing about a gallon of water.