Make sure you soak the pellets completely before you feed them to him. Dry pellets expand in the fish's belly, which could cause bloat or constipation. Also, his stomach is the size of his eye, 2 pellets twice a day should be more than enough.
You definately want to do 100% water changes once a day. My fish was in a 1/2 gallon tank for several months, and even with daily water changes, he would develop fin rot, and then he began to tail bite. Don't expect your fish to be active in such a tiny tank. At all. My fish as a sitting lump for the few months he was in the 1/2 gallon tank. When I upgraded to a 10 gallon tank, he was suddenly acting like the energizer bunny.