Aquaponics fish. Image Credit: Biodiversity Heritage Library (Flickr)
March 19, 2018 Fish 5,046 Comments

Numerous things go into maintaining the healthy aquaponic fish – good feed, correct temperature and water quality.

Having knowledge of the basic anatomy of your fish will help you identify abnormalities that can lead to disease in otherwise healthy groups of fish, as well as helping you distinguish between the sexes. Also, being able to name various body parts will allow you to easily identify problems using reference materials. So what does a healthy aquaponic fish look like? Read on!


The fins are made of rays covered by skin. Different breeds may be jointed and some separate near the edge of the fin. Some fish have bony, unjointed and stiff rays and these are referred to as spines. Each fin on the fish has a purpose.

Dorsal fin – this is the one at the top on the back, most fish have one of these. Sharks have a particularly alarming one that sticks above the water when it swims near the surface…if you’ve seen Jaws you will know what this means! The function of the dorsal fin is to lend stability in swimming.

Ventral fin – his is a pair of fins that sit on the underside of the fish, they are also sometimes known as pelvic fins. They assist stability in swimming.

Caudal fin – also known as the tail fin, this acts as the propeller to move the fish forward while swimming.

Anal fin – as the name suggests, this sits between the anal region and the tail fin. Its purpose is to lend stability in swimming.


Image Credit: Biodiversity Heritage Library (Flickr)

Image Credit: Biodiversity Heritage Library (Flickr)

The skin of the fish has two layers. The outer layer (epidermis) and the inner layer (dermis). The epidermis is made up of cells that are continually shedding and being replaced with new ones. In-between these are slime cells which produce a mucous like secretion that form an important protective covering, usually called the slime coat. This is why fish often feel a bit slimy to the touch.


The dermis of the skin is made up of collagen, blood vessels and connective fibroblasts. The scales lie in small pockets within the dermis. They do not stick out but are covered by the protective slime layer. They overlap each other and make up a protective armor meaning the fish is able to withstand a certain amount of bumps and blows. Some species have serrated edges on their fins, and others are smooth. Some species have bony plates in the place of scales and some species do not even have scales at all.


Lots of fish have very pretty coloring and patterns. These are produced by cells in the dermis.

Fish can change color and changes are often seen during mating, survival and feeding. This is due to a movement of melanin grains within the cells.


These are the means of respiration in the water and are found under the gill covers. They are five slit-like openings in the walls of the pharynx, in which a delicate system of blood vessels extracts gases from the water.

Lateral Lines

The lateral line is a series of scales that are used to detect movement and vibrations in the surrounding water. It runs in a half line from the gills to the tail fin and is easily identified as a band of darker looking scales down the side of the fish’s body. It is a very important sensory organ for the fish.

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Written by Pippa Woodhead
Being a health-nut, London born Pippa has struggled to adjust to the lack of availability of lettuce and kale since re-locating to India. Previously naive to the extent of the worlds food struggles, she has now become obsessed with sustainability in food production and especially in India where it needs it the most (plus she’s also hoping to get her hands on some kale any day now). When she’s not writing for Aquaponics in India, she is usually found with her head in a book or in the kitchen experimenting with new vegetarian recipes.