Feed in tiny portions.While many people have heard that fish require a "pinch" of flake food each feeding, giving them too large a pinch can give the fish digestive problems or make the tank dirty and unhealthy. Whatever type of dry food you are using, only put in as much food as your fish can eat in 3 to 5 minutes. If you put too much food in the tank, scoop it out with a fine net.
Warning: Betta fish should be fed much less than they can eat in 5 minutes. Two or three small pellets per betta is sufficient.
Soak pellet foods before feeding. Because many aquarium fish have small stomachs, pellets that absorb water and expand in size may cause digestive problems or bloating in your fish. Soak the pellets in water for 10 minutes before feeding so they expand before the fish eat it, rather than in the fish's stomach.
Feed the fish once or twice a day. Because it is much easier to overfeed most fish than to give them too little food, one feeding a day may be safer. However, if you are careful to give them small amounts of food as described above, you may feed the fish twice a day. Some aquarium owners prefer this because the fish become more active and interesting to watch during feeding.
Look for signs of overfeeding. If a trail of poop is hanging from your fish, their intestine may be partially blocked due to overfeeding or the wrong type of food. If the water gets dirty enough that you need to do a water change more than once a week, you may be overfeeding the fish, or the tank may be overcrowded. Reduce the amount of food per serving or the number of servings per day to see if the problem goes away within a few days. Ask an aquarium store employee or fish raising hobbyist for advice if it does not.
Spread out the food so everyone gets some. Even within the same species, the larger or more aggressive fish may not leave enough food for the other fish. Reduce the chance of this happening by dividing the food and adding it to more than one area of the tank, or by sprinkling it evenly across the entire water surface.
Watch for problems if you have multiple types of fish. If you have fish in your tank that feed in different areas of the tank, or on different types of food, you will likely need to purchase more than one fish food. Watch mixed-species tanks closely during feeding when you start them on a new food. You may need to find different combinations of food or feeding times if the fish at the surface eat all the food intended for the fish at the bottom. If some of your fish are active during the day and others at night, feeding them at two different times may help ensure that each fish gets enough food.
Consider your options while away on vacation.Leaving adult fish alone without food for a few days is almost always safe, and if you research your fish species online you may discover they can survive without serious risk for one or two weeks. For longer trips, or for young fish with more urgent food requirements, you'll need a way to feed them while you're gone. Choose from one of the following solutions:
Use an automatic feed dispenser to dispense food at regular intervals. Make sure you supply enough food for the whole time you'll be away, and set the dispenser to release food once or twice a day.
Test a feeder block or gel feeder before leaving. These blocks of dry or gel-covered food are left in the tank and eaten slowly. However, the dry blocks may cause dangerous chemical changes, while the gel variety sometimes go ignored. Test either variety for a few days before leaving so you can be sure there are no problems.
Have a friend or neighbor feed them their usual flake food once every two or three days. Because inexperienced feeders often give too much food, it's best to place each pinch of food in a pillbox or other container with the day of the week carefully marked on it. Make it clear to the caretaker that overfeeding could kill your fish.