The inland water bodies consist of small aquariums to nursery ponds, canals, beels, haor, baors (oxbow-lake), rivers, streams, flooded lands, etc. These are called freshwater basins. The more diverse fish types are found in these water bodies. The shape, nature, feeding habits, color, etc. vary from species to species. Their cultivation system is also different. It is important to have scientific knowledge about the nature of fish, feeding habits, diseases and so on to cultivate fish through the choice using suitable control measures. Food and feeding habits of fish is very important factor that helps to choose the fish type for cultivation.

Types of Fish

Fish are classified into the following four types based on the type of food.

Herbivorous

This type of fish survives, grows and reproduction by eating unicellular algae, filamentous algae, small water plants, portion of higher aquatic plants, detritus along with some mud or sand. In this case, the plant materials in their food consist of about 75% or more of the total gut contents while the animal-based food varies 1-10% in its diet. For example, Labeo rohita, Catla catla, Labeo bata, Ctenopharyngodon idella, Amblypharyngodon mola, Oreochromis mossumbicus, etc.

Carnivorous

They take large numbers of animals as food such as Copepods, Cladocerans, insects such as beetles, water bugs, damsel flies, dragon flies, larvae, mollusks, different small fishes, tadpole larvae, etc. Some notable carnivorous fishes are Wallago attu, Channa punctatus, channa striatus, Channa marulius, Channa gachua, Chitala chitala, Chanda nama, Chanda ranga, Rita rita, Glossogobious giuris, Mystus seenghala, Mystus cavassius, Ompok pabda, etc. Among them some are active predators such as Channa marulius, Channa striatus, Wallago attu, Chitala chitala, Mystus seenghala, etc.

Omnivorous

These types of fish eat all kinds of food. Although their favorite food is insects, they also eat vegetable-based foods such as unicellular and filamentous algae, different aquatic plants when needed. Besides, they take zooplankton such as crustaceans, rotifers, insects and its larvae, mud and sands. During their young stage, most of the fish prefer to eat zooplankton. They consume varying percentage of plants and animal materials.

Among omnivorous fishes, some feed on a large amount of plant materials. Some feed on equal amount of animal and plant materials while other take a greater amount of animal foods. Some important omnivorous fishes are Cyprinous carpio, Cirrhinus cirhosus, Tor tor, Puntius ticto, Puntius sophore, Puntius sarana, Gadusia chapra, Colisa fasciatus, Eutropicthyes vacha, etc.

Plankton Feeders

Some fish species take both zooplankton and phytoplankton. They take these types of food by filtering water using their gill rackers. Gizzard shad (Dorosoma cepedianum) fry feed on zooplankton until reach the length of one inch. They become a filter feeder after losing their teeth and consume phytoplankton and some tiny invertebrates.

Menhaden (Brevoortia) is also filter feeder that prefers to feed mainly on phytoplankton. They capture phytoplankton from the water using their gill rakers. Adult menhaden can filter 4 gallons of water per minute and receive different phytoplankton and zooplankton within their gills.

A silver carp (Hypophthalmichthys molitrix) is also a filter feeder that has a special filtration capacity. They can filter though their gills and consume lots of phytoplankton and zooplankton.

Fish can also be classified into the following three types based on the niche they occupy in different water levels.

Surface Feeders

The uppermost layer of water, where sunlight enters, grows a large number of plankton which produce their food through the process of photosynthesis using their chlorophyll. At this level oxygen is even higher which is suitable for various animal organisms. Catla catla is mainly stay at this level to collect food. Silver Carp is also a resident of this level. Besides, Puntius ticto, Oygaster bacaila, Chanda ranga, Chanda nama, Glossogobious giuris,Tenualosa ilisha, Gadusia chapra, etc are notable surface feeder fishes.

Column Feeders

Some species of fishes take their food from the mid water. At this level water waves are relatively few but zooplankton, phytoplankton are available with sufficient amount of oxygen, suitable for fish. The fish that live here are neither true bottom nor true surface feeders. They mostly depend on the food of the middle layer of the water. Labeo rohita, Labeo bata, Tor tor, Puntius sophore, Mystus seenghala, Wallago attu, Mystus vittatus, etc are the column feeder fishes.

Bottom Feeders

The bottom feeder fish mainly depend on food for bottom organisms. At this level, lots of benthos live here that provides nutrients to the fishes. Labeo calbasu, Labeo gonius, Cirrhinus cirrhosus, Puntius sarana,Amblypharyngodon mola, Cirrhinus reba, Clarias batrachus, Heteropneustes fossilis, Channa striatuis, Channa marulius, etc are notable bottom feeder fishes.

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The following table showing the food and feeding habits of some freshwater fishes:

Scientific Name of Fish	Order Name	Feeding Habits	Food Types
Mystus seenghala, Wallago attu,	Siluriformes	Carnivorous and Predatory	Fish fry, insects and its larvae, fingerlings, small fishes, tadpoles, frogs, etc.
Channa marulius, Channa striatus, Chitala chitala	Cahnniformes	Carnivorous and Predatory	Fish fry, insects and its larvae, fingerlings, small fishes, tadpoles, frogs, etc.
Clarias batrachus	Siluriformes	Omnivorous	Insects, worms, crustaceans, fish fry, insects larvae, decaying organic maters, etc.
Heteropneustes fossilis	Siluriformes	Omnivorous	Insects, worms, copepods, ostracods, debris, algae, etc
Labeo rohita	Cypriniformes	Herbivorous	Algae, microscopic plants, vegetable matters, detritus, sand and mud, etc.
Osphronemus goramy	Anabantiformes	Herbivorous	They mainly feed on aquatic plants and algae.
Oreochromis mossambicus	Cichliformes	Herbivorous	They mainly feed on aquatic plants and filamentous algae.
Ctenopharyngodon idella	Cypriniformes	Herbivorous	They voraciously feed on aquatic vegetation.
Hypopthalmicthys molitrix	Cypriniformes	Plankton feeder	Unicellular algae, rotifers, decaying microorganisms, detritus, etc.
Catla catla	Cypriniformes	Plankton feeder	Microscopic plants, Algae, rotifers, insects, crustaceans, etc.
Cirrhinus cirrhosus	Cypriniformes	Omnivorous	Algae, decaying plants, and animal matters, detritus and mud, etc.
Tor putitora	Cypriniformes	Omnivorous	Algae, decaying organic matter, insects, rotivers, protozoans, etc.
Tor tor	Cypriniformes	Omnivorous	Macro vegetation, filamentous algae, mollusks, sands and muds, etc.
Cyprinus carpio	Cypriniformes	Omnivorous	Algae, macro-vegetation, insects, rotifers, crustaceans, etc.

Concluding Remarks

Food and feeding pattern of fish is very important factor that helps to choose the fish type for cultivation. It helps to avoid clash for getting food among them in different water levels. Fishes are carnivorous, herbivorous or omnivorous however a large portion of them are exceptionally adaptable in their feeding habits and use the promptly available diet. Just a few fish groups are strictly herbivorous or carnivorous and the available food helps to decide if it will be eaten by the fish.