How To Deal With Deformities In Tank-Raised Fish: Common Causes And Guidelines 2023

UP: This Altolamprologus calvus “White” has the entire plate that covers the gills missing.

MIDDLE: This Altolamprologus calvus “Yellow” has a misshaped head and is missing part of the plate that covers the gills. It also has Goiter. Goiter is a swelling in the throat of the fish that restricts feeding which can cause the fish to starve to death.

BOTTOM: This Altolamprologus calvus “Black” has a misshaped head (face twisted sideways) and Goiter.

While there is still some argument about the causes of deformities in tank-raised fish, there is no doubt that they are a plague to the aquarium hobby. Some things we can do as conscientious fish keepers are to avoid buying fish from stores or wholesalers that consistently sell deformed specimens and to carefully cull any even slightly deformed specimens out of the fish that we produce.

First, let me cover the common causes of deformed fish. There are two major causes: the first and probably most common is genetic defects. These defects are caused by the poor selection of breeding stock. Fish are more prone to genetic defects the farther out of the wild they are bred. You are also more prone to genetic defects if you or the person you received the fish from either don’t select the top quality specimens or breed too closely to the same genetic pool. The second most common reason for deformity is the cross-breeding (interbreeding of two different species) of fish. This does not happen too often however you will occasionally run into this. There are some tell tale signs of this that I will cover later. There are other reasons that deformed fish are produced and these can range from overfeeding of fish to increase growth rate. This can also occur if a food that is to rich in proteins and fat is used. The opposite can also occur, underfeeding of fish can result in fish whose growth is stunted. This is often harder to detect at first as most of the time you do not know the age of the fish when you purchase it and even if you did it would be awfully hard to memorize the approximate growth rates of so many species.

The first step in either preventative measure is to be able to identify deformities. The best method of this is to have good knowledge of what the fish that you intend to keep looks like. One good source for this type of information is books. Books often have good accurate representations of what particular species are supposed to look like. Another good source for information is the internet. However, I would personally recommend looking at several websites and getting a compilation of information from them. Unlike books who usually have a technical editor or who are written by someone who has a vast amount of knowledge on the subject they have written about, anyone can put up a website. While most of these websites have good intentions they may have limited knowledge of what species they have and many are limited to nomenclature of species or common names that they purchased their fish under. If you do not have access to any of this information or cannot find information on the fish that you wish to purchase, there are a couple of other guidelines that you can use.

These guidelines include studying the other specimens of the same species that are in the tank. You need to look for a consistent body shape. All fish of the same species should have the same body shape. You can also study differences in barring patterns and coloration. This is a little more difficult in most fish because you must take into consideration subdominant coloration and barring patterns, female coloration and barring patterns, as well as fright patterns for the particular fish species. As you can see this is a little more difficult proposal. These methods are often employed in verifying correct identification in species where the females of several species or even just regional variants are very similar particularly in wild caught fishes. It is best when acquiring wild caught fish to sell that you raise the first batch of fry to a size where the males are fully colored. Then you will be able to tell if your fish have crossbred. If the males of the fry are identically colored to the father they are a true species more than likely.

Now we can cover the proper techniques for breeding stock selection. The best way to establish a breeding colony is to buy many juveniles preferably from different sources. You should always make sure you get your breeding stock from people or businesses that have the best quality fish, even if you have to pay a little more. It would be better to get all of your stock from one source than to get stock that is not high quality. It is best to grow your stock up to at least young adult size. If you have purchased your stock from multiple sources it is important to keep the specimens separated in order to be sure of the genetic diversity that you want. Once they have reached the proper size select females from one set of fish and a male or a couple of males from the other set of fish. When selecting your breeding group. You have a couple of options depending on what you want to breed for, most commonly in most species of fish you would want to select specimens that are as close to their wild-caught relatives as possible. This should include size, coloration, body shape and barring patterns. Barring patterns in most species should be straight with no irregular shapes and should match exactly from one side of the fish to the other.

As far as being able to tell if a fish has been overfed or stunted. These problems are even more difficult to detect. Overfed fish will often exhibit characteristics of genetic deformities. The most common characteristic that I have seen in juveniles from overfeeding is a fish that looks stumpy (growing taller and broader than it should be for a given length.) These fish usually have a significant amount of fatty deposits. These fatty deposits can cause health problems in fish. They can also cause problems with breeding. Stunted fish is the hardest characteristic to recognize. The easiest way to determine this is in fish that have different adult coloration than juvenile coloration. If you see a fish that is exhibiting adult coloration at a smaller size than is usual for the species this is often an indication of growth problems. Of course this means that you must know about what size the fish colors up. There is one more thing to cover that doesn’t really have to do with deformities but it does related to being able to buy fish for breeding purposes.

This is fish marketing. Unfortunately in this day and age of wanting to make more money off of their fish-related business, some breeders and wholesalers have resorted to either changing fish names or adding fancy superlatives to the names of their fish. As far as changing fish names I have seen everything from reverting to older scientific names that are no longer in use to just changing the names of the fish entirely. I have seen wholesalers use names like super red top for wild caught fish, even though they are collected from the same location as every fish of that species that everybody else is selling. This is an obvious attempt to make their product seem superior by using fancy names. As far as an example of changing names entirely. There are a group of African cichlids known as peacocks that has a red strain that has been developed in the aquarium hobby. Some breeders/wholesalers use several different names for the same fish. These names range from Ruby Red to German Red to Rubensens to Ruben Red and recently they have even added another name of Chidunga Rock. The last of which is just the collection point of the fish that originated the red strain. This attempt at deception in the aquarium hobby only makes it hard to keep track of which fish are which.

Just keep in mind the person who is selling the fish might not be the best person to ask about the quality of their fish. I have heard a wide variety of excuses for deformities in aquarium fish. Examples of what I have heard are anything from there was too much water current in the grow-out tank and that is what caused their face to be rounded to the females applied too much pressure to the fry while they were in her mouth for mouthbrooding fish to account for a wide variety of body shape problems. I have even heard an excuse of sand irritating the gills to explain why you could see red in the gills of fish when really part of the plate that covers the gills of that fish were missing(See photo).

So as you can see selecting good quality breeding stock can be quite difficult and relies on knowledge on the part of the breeder to select good quality stock. So if you want to get into breeding fish it is important to get out and seek information on any species that you wish to breed. If at all possible try to see as many examples of the species you want to breed as possible. This will give you a better idea of the quality of the fish that are available to you. It is you as a fish keeper who is going to determine the future of this great hobby by buying your fish from businesses or hobbyists that only deal in top-quality fish and by carefully selecting any breeding stock.

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