There is no ideal time of day to feed aquarium fish. Timing is not critical except in the case of nocturnal feeders such as certain catfish, which should be fed before the tank lights are turned off.
In general, most fish do well on one small feeding a day, though some fish owners prefer to feed twice a day in very small quantities. Most fish only eat what they need to survive. In tanks, fish actively eat for two minutes and then ignore the remaining food, which falls to the bottom of the tank and is wasted. Overfeeding can clog the tank’s filter and produce excess nitrates that are harmful to the fish.
However, fish that are herbivores need a more structured feeding schedule because their stomachs cannot hold large amounts of food. Owners of these fish should give several small feedings at various times throughout the day. Another solution is to provide live plants on which they can graze and nibble.