Like most other animal groups, fish have developed requiring a variety of diets. There are carnivorous fish, which require mostly animal protein in their diet, there are herbivorous fish, which have a high level of plant matter in their diet, and there are omnivorous fish, which require a good mix of dietary components.
How do I know what diet my fish requires?
Diet is determined by the type of fish. The types of fish that are commonly kept as ornamental aquarium fish have been studied closely over the years, and there are many references avaialable to find out the specific dietary requirements of the fish that you have selected. In general, the information will have been collected from studies of the fish in their natural state and then this information can be used to help you select an appropriate food type.
The science of fish nutrition has progressed rapidly over the years and there is now an array of diets that we can purchase to feed to our Piscean friends. So, now armed with the information regarding generally what your fish would eat in the wild, you can make some informed decisions as to what type of commercial diet is suited to your fish. Flaked, pelleted, frozen and live diets are available.
The most common type of diet is the flaked food. This is made by cooking and drying a mixture of components, which end up looking like pancake mix. Once it is dried it becomes a thin pastry, which is easily presented to the fish. It is readily digestible by the fish and has become the staple diet for most aquarium fish. There can be many components added to the food, which make some suitable for herbivores whilst others are for carnivores or omnivores. So 'flakes ain't flakes' as they say. That's why if you visit your local aquarium shop you will find great selections of bottles of foods produced by various companies, which can all be a bit confusing. Now this is where you use your knowledge of what your fish will eat in the wild and your ability to read the labels on the bottles. Most diets will have listed on the label for which fish the diet is suitable. Your research will allow you to confirm this suitability.
Pelleted diets are similar in composition to the flaked diets, but they allow more nutrition per bite than the flakes. The decision as to which one will be suitable is the same as for the flaked diets; it's just that your fish will have to be a bit bigger so they can actually eat the pellets. The general rule of thumb for pellets versus flakes is based on the size of the fish. Small fish eat flakes and big fish eat pellets. Now that's not to say big fish can't eat flakes, it's just that you'll have to feed them a lot more to gain the same amount of nutrition as a few pellets.
The other commercial diets that are available come in the form of frozen diets. These diets are commercial formulas of raw ingredients that are finely minced and combined before being frozen, and are presented in sealed cubed packs to allow portions to be easily dispensed. They come in a variety of formulations and it is simply a matter of selecting a diet that has been suitably designed for your fish. Diets such as frozen brine shrimp or bloodworms allow a good source of highly digestible protein and can be used as a treat or supplement.
Live foods can also be given to fish, and at some stages of the lifecycle these feeds are an essential part of survival for many fish. The movement of the food is a stimulant for feeding in many small fish fry and once the fry have excepted live foods it is just a matter of weaning them onto commercial diets for a balanced nutrition. Live foods can be harvested or grown from cultures. There is less likelihood of introducing disease from cultures and so despite more hands on involvement this would be the method of choice. Cultures of wingless fruit flies, numerous types of nematode worms, brine shrimp eggs and even garden worm cultures can all be propagated to add that little something extra that can’t be found in dry diets.
Once you have chosen a suitable commercial food, whether flaked, pelleted, frozen or live, to meet the dietary requirements of your fish, you need to feed the correct amount at the appropriate time.
When should I feed my fish?
Fish are creatures of habit. They like to eat at the same time of day each day. This means that when you feed them they are likely not to waste the food if they are fed at their allotted time. Once a day is fine for most fish, however, if you are keeping the more herbivorous fish, smaller feeds more often should be the rule.
How much should I feed my fish?
Most sources quote that you should feed about as much as your fish will consume in a 5 minute sitting. This really is to protect the tank more than the fish. If you pile in a large amount of food into the tank that the fish cannot find and will not eat, it just serves to foul the tank, negatively effect the water quality, and ultimately cause health problems in your fish. So stick to the five-minute rule and if, in time, your fish look in poor condition, rather than fed them more at a sitting, just feed them more often.