No, a fish will only eat until its hunger is satisfied. HOWEVER, if you overfeed your fish, the uneaten food will eventually start to pollute the water, and THAT can cause the fish to die. Fish prefer frequent, small meals, but you can easily get away with feeding them once or twice a day. Just make sure you don't give them any more food than can be consumed in 5 minutes. Also, the larger fish probably has a slower metabolism, so it may not require as much food as the smaller fish.