This article is particularly aimed at people new to the hobby where overfeeding tends to be more common, and gives a guide to feeding the general community fish that we tend to start with.

It is not that we intentionally mean to 'overfeed' but I think we've all walked past our aquariums especially in the earlier days seen the fish swim up, so we thought we?d add a pinch of food just to make sure.
Fish in the aquarium environment is like us living permanently in a hotel, after a little while of enjoying the luxury of having lovely meals put in front of you, one would have to 'cut back a bit' or you would be gaining weight. A fishes appetite is much bigger than it's stomach, your fish will continue eating long after they are full and the food simply passes through polluting the water.
Human beings are hot-blooded, meaning we have to get energy in form of food in order to maintain and stabilize our temperature. Fish are cold blooded, their temperature is controlled by the environment they're in. The metabolism of fish is controlled by their surrounding temperature. The lower the water temperature, the lower their digestive time. Generally speaking, the digestive time for fish kept in 74-78 degrees is about 16-24 hours if you try to remember this you won't go far wrong.
Consequences of overfeeding :oops:

High ammonia and nitrites - The protein in uneaten food and fish waste is broken down into ammonia and nitrites, which are toxic to fish and we would need to increase water changes to keep these levels low.

Low oxygen levels - When organic material (uneaten food and fish waste) decays, it is an aerobic process, meaning it uses oxygen and produces carbon dioxide. This means there is less dissolved oxygen in the tank for the fish. Fish will come to the surface gasping for air, an airstone may have to be added to the tank.

Low pH levels - Just as the breakdown of organic material lowers the oxygen level, it also lowers the pH of the water because acids are produced during the process. Since each species of fish has an ideal pH range we should aim to keep them in the correct conditions.

Fin rot - Fin rot is a condition in which the fins can develop an untidy, ragged appearance. It most often occurs when fish are stressed and water quality is poor, which is a common result of overfeeding.

The dreaded Algae - Algae growth is one of the most common problems seen in aquariums. The number one cause is overfeeding, algae will thrive in any aquarium where plenty of excess nutrients are available.

Planaria (flatworms) - Planaria are small white or tan worms that are good indicators that water quality is not optimal. They are most often found in tanks where overfeeding has occurred. Although generally considered harmless, they will eat fish eggs and do not look very nice, cut back on feeding, give the tank a good clean not forgetting to siphon the gravel (I hate these).

Clogged filters - Filter systems are designed to remove the normal amount of waste materials and breakdown products from the water. Uneaten food and waste materials will collect on the filter pads/sponges and clog the filters and reduce their efficacy. If your pads are saturated in brown slimy gunk in a couple of weeks, then you are overfeeding.

A Fish Feeding Routine

Feed on a schedule - Most tank inhabitants will do well if fed twice daily. If possible, more frequent and smaller feedings are preferred. In the wild, most fish do not eat large meals like we do, but are foraging and grazing throughout the day, so simply divide the daily amount into smaller portions.

There are lots of live/frozen foods available from your LFS, these should be given only as a treat no more than a couple of times a week.

How Much Then :book: - The best way to determine how much to feed your fish is to watch them while they feed. Add small amounts of food at a time, just 2-3 flakes. If all the food has been eaten within several minutes, feed a small amount more. The general rule of thumb is to only feed them as much as they can eat within 2-3 minutes. Anything not eaten by then, will likely never be eaten and really should be removed as it will start to break down.

If you think you have put too much food in the tank, perform a partial water change by siphoning 25% of the water from the bottom of the tank. Use the siphon to pick up as much debris/food from the substrate as possible.

Make sure all the fish are feeding and swimming normally, it's a great time to look for anything that may be cause for concern

Research the feeding requirements of the different fish you keep - Different fish require different foods. There are top feeders (upturned mouth), mid-water feeders, and bottom feeders (mouth on the underside). Hence, floating foods, slow sinking foods, and rapidly sinking foods, something for everyone.

Fish are creatures of habit and may take time to identify a new food as something that can be eaten, so just add a little until they get used of it.

Bottom feeders - Scavenger fish (catfish and loaches) and invertebrates can assist in 'cleaning up' some of the uneaten food that falls to the bottom of the tank. They can be helpful in removing food that falls to inaccessible areas of the tank that may be difficult to siphon or clean, but beware foul conditions/rotting food on the substrate will not keep these fish in good condition they need a good, clean environment also.

Tip...and perhaps the most important one!
As a general rule a fishes stomach is about the same size as it's eye so as you can see when looking at your fish they don't need much food!

Remember overfeeding is the major cause of fish loss.