When compared to humans, the digestive system in fish is relatively simple. There will of course be variations that are species-dependent. Some species of fish have teeth. The teeth in fish are generally adapted for performing special functions. Predatory Catfish will for instance have small sharp pointed teeth, while the Pacu fish have teeth adapted to crushing fruits and nuts.

The stomachs of fish are also generally adapted to the kind of food they eat. Predatory fish generally have sac shaped stomachs that allow them to pack away enormous amounts of food. The Puffer fish has a stomach that can be inflated with air or water in order to scare off enemies. Food that is partially digested moves from the stomach into the intestine. Here it is digested further and the nutrients are absorbed into the body. The herbivores have an elongated intestine and their systems are more complicated than the carnivores. Food that is not completely digested and absorbed leaves the body through the anal opening, together with other waste products produced by the metabolism.

Giving your fish the right kind of food at the right time and in the right amounts is crucial to their growth and development. In a closed system, the fish have no choice but to eat what they are provided with. If you want fish that are full of energy, you have to feed them according to their particular needs.

– Every type of fish has a specific feeding requirement. Herbivorous fish require lots of fiber in their diet, while carnivores require food that is rich in protein. Some predatory fish eat food only after chasing the live food.

– Do not make your fish obese. Yes, fish also gain unhealthy fat from over eating. Some fish like the catfish will eat just about any amount of food. They become too big and lose health. Remember that fish in your aquarium do not expend energy looking for and chasing food. They only move about within the confines of your tiny little aquarium. So, feed your fish only according to their nutritional needs.

– Overfeeding introduces a lot of unwanted toxins into your system. Mostly, fish are able to take in the food they need within 5-10 minutes of their feed. Food left in the aquarium after the first 10 minutes of feeding is not needed by the fish, and will collect in the aquarium as waste; decaying and releasing toxins.

– Obtaining food can become a problem in a community or biotope aquarium at times. Hyperactive fish and fast swimmers will get the first pick in the aquarium. Small fish can be scared away by larger fish and newly introduced fish may be too shy to get to the food.

– Give your fish a variety of food. Feeding fish the same kind of food day after day tends to dry up their appetite. Besides, they also need a variety of nutrients, which can be provided only by rotating the feed.

– Be very careful when and if you introduce live food into your aquarium. Many fish species love worms, insect larvae etcetera and will stay much healthier when provided with live food. Care must however be taken to ensure that these food varieties do not carry infections, such as germs or other parasites, in them. This is very difficult to ascertain, unless you culture your own live food. So beware when you feed live food to your fish.

Food for the fish has to encompass a large number of nutrients. All these together make your fish healthy and able to adapt to changing conditions in the aquarium. Remember, the healthier the fish, the more resistance will they have to disease and infections.

Protein and fish

Protein is the single most important nutrient that the fish needs to grow. On a dry-weight basis, this makes up the maximum weight in their body structure. Amino acids are derived from proteins and the fish uses them to make new body tissues as well as enzymes. Fish are very adept at converting food to body tissues. That is why fish need lesser amounts of food than do most other animals. Carbohydrates are almost non-existent in the food intake for many fish species, since energy is also derived from proteins.

The quantity of protein required for the fish to be healthy depends on a number of variables like the species of fish, amount of natural food available, growth rate etc. Fry and larvae require a more protein rich diet to maximize their adaptability and chances of survival. As the fish grow larger, their dependency on protein reduces. The temperature of the water also affects protein requirements.

Fatty acids and fish

Fatty acids are a storehouse of energy for most fish. They provide stamina. Carbohydrates can also do this job. It is also seen that some of the predatory fish species require some source of fish oil in their diet too. Fish that live within the confines of an aquarium are naturally prone to obesity. They do not use up their excess energy in swimming long distances or looking for food. In most cases, excess fat can be damaging to the general health of the fish. Some fish lose their reproductive capabilities if there is too much body fat.

Fat-soluble carotenoid and fish

Fat-soluble carotenoid is responsible for the bright hues in some fish. Krill and brine fish are some of the foods that are rich in pigments.

Carbohydrates and fish

Carbohydrates make up 20-30% of the common commercial foods. While they are alternate sources of energy, they are not very necessary for fish growth. Though most fish will handle some amount of carbohydrates, they develop signs of ill health if there is a high concentration of carbs in their diet. For instance, if young fish ingest too much of carbs, other nutrients will not be absorbed appropriately by their bodies. That is why cereal grains, which have very high levels of raw starch, are not ingested fully by fish.

Vitamins and minerals and fish

Vitamins are vital to fish health. These are organic substances that act as catalysts for many of the biochemical reactions within the fish. Almost all vitamin deficiency will increase the fish’s susceptibility to diseases and stress. The best way to get a rich supply of vitamins to your fish is to buy small quantities of diverse food for them. Storing excess food in the freezer also prolongs the life of the vitamins. Providing frozen or fresh vegetables and live food can also supply the much-required vitamins to your fish.

Minerals are also necessary for you fish. Bones, teeth and scale tissues require lots of minerals. The minerals also carry out many supportive functions. Your tropical fish will most likely suffer from a lack of Calcium and Phosphorous, if any. If they are kept in hard water, fish are able to extract some amount of calcium from it, but soft water has absolutely no supplies of calcium. Though mineral supplements will help to compensate this deficiency, excess of some minerals can be poisonous. Therefore, mineral supplements should not be used indiscriminately.