Overfeeding fish can have devastating effects. Uneaten food and excessive waste production can poison them to death. As a rule, your fish should be fed no more than what they can eat in 3 minutes; in most cases, a single daily feeding is adequate. If there's too much food in the tank, use a fine net to scoop out uneaten flakes and pellets; a siphon hose will vacuum up smaller particles.
For more information, please click on How Much Food is Too Much