Breeding Aquarium Fishes

Updated during November, 2023.

Warning! This article includes personal opinions and speculations!

This is an introduction, with tips that I hope can help you on your journey to become a good, or better, fish breeder.

For starters, you can think of what species of fish you want to breed. Investigate if it is a suitable species for you to breed. Some species have never been bred in captivity, while others are so easy to breed that they spawn even if you don't want them to.

Is your tap water suitable for the species you intend to breed? If not, can you easily make adjustment to the water to make it more suitable, or obtain water from somewhere else? If not, then perhaps it is advisable to choose another species that is more compatible with your tap water?

It is a huge advantage if you can easily sell, or trade, the offspring after you have raised them. It is not just about economics, but also about making sure that there will be someone willing, to accept and take care of the fish you raise, since you might not have enough aquariums to be able to take care of all of the offspring yourself, when they fully grow up. It is a good idea to find out about the demand and the potential market price. Be aware that you might end up with a lot of fish, that maybe no one wants, perhaps not even for free, if you choose a fish with low demand, or an already flooded market.

When you have chosen what species of fish you want to breed, you should make sure you have a suitable aquarium for the purpose. If you do not already have a suitable aquarium, you can consider buying an aquarium in an aquarium store, or hire someone to build you an aquarium. Perhaps you want to build one yourself, or try to get one cheaper second hand? Take a look at the policy of your insurance company before you decide, some contracts demand that the aquarium needs to have been built by a professional, to pay anything in case of an accident.

If you buy an aquarium second hand, you should make sure that the quality is high and that it is not leaking, unless you are handy and experienced with repairs. Be aware that, for some species you may require more than one tank to raise them, especially species that are cannibalistic, and/or very competitive for food. You may need several more tanks to grow the fish out, or you may need to put dividers in the tanks, to separate the fish according to size (and sometimes gender), as they grow.

Decorate the aquarium after the demands of the species. When you have all the equipment you need and the aquarium has cycled, it is time for the fish. I believe it is important to get hold of breeding stock of top quality. It is, usually, good to obtain about six to ten young ones, that can pair up while they grow. (That is, if you have chosen a species that develop pairs. If they are shoal spawners, it is also, usually, good to start with this number of fish.)

To get suitable fish at a reasonable price, it is an advantage to have connections with other fish breeders. From them, you might be able to select specimens of extra high quality from several different batches and different parents. You can easily get connections with fish breeders through an aquarium society, sometimes called an aquarium association, or a fish club.

You can also buy the fish in an aquarium shop. There are a few things that you should be aware of, when buying fish meant for breeding, from an aquarium shop. I am not talking about price. There are limitations, such as that you, probably, don't get to see the parents of the fish, or previous generations. It also comes with, generally, higher risks, concerning fish health, as the fish are more likely to carry diseases, as an aquarium shop is a very difficult place to keep completely free from fish diseases.

There are often many new and stressed fishes arriving to an aquarium shop. Some aquarium shops put all, or most of, their new arrivals through quarantine, and/or medication. Other aquarium shops simply add all the new arrivals directly into the ordinary "selling aquariums", while "hoping" that all the new fishes come from wholesalers that have already done sufficient quarantine procedures.

An aquarium shop is often the best place, or only place, where you can easily get hold of certain species and varieties. It is naturally possible to get breeding stock from aquarium shops. However, usually, the best fishes get sold first in an aquarium shop. You may have to befriend someone who works there, and/or owns the shop to help you out. Maybe you can make a reservation on a new shipment?

I suggest that when you do buy fish from an aquarium store, it should preferably be from a good shop with staff that have true aquaristic knowledge. You should also ask about what they know, or suspect, of the origin of the specimens that you choose. Write it all down for future reference. It is also good to be able to provide this information about the name, origin, pedigree, or lineage, when you later want to start selling, bartering, or giving away the offspring of these fishes, that you plan to raise. Try to avoid mixing pure strains, unless you have a reason to do so.

Generally, try to avoid buying fish from the "bottom scrap", that is left after other buyers have already taken their pick of the best specimens. You should be one of the very first to choose from the fish that arrive to the shop. (The cream of the crop, the pick of the litter, so to speak.)

If you don't want to personally deal with the high risks involved when buying newly arrived fish, you should try to book them (if necessary, pay in advance or make a down payment), but let the aquarium shop quarantine them, before you take them home. You need the best starting material you can get, so you also get high quality offspring from the fish. Do not be afraid to pay extra, if needed, to get healthy fish of excellent quality for breeding, it will be rewarded later.

Sometimes, wholesalers have different grades, sizes, or color variants, that the aquarium store, usually, does not order, because they are more expensive per fish. Ask the owner, or the employee, at the aquarium shop, if they have any lists from wholesalers and if there are any other options available on those lists, of the specific species that you want to breed.

There are also many species that do not color up at all when young. It can be difficult to choose potential breeders from them. Both you and other potential buyers have this problem. It may be a gamble to choose a larger group of them and buy them before they color up. Sometimes, gambling this way, is the way to go.

If you wait for the fish to color up in the aquarium store, there is a high risk that someone else might buy the best ones as soon as they color up and you miss the opportunity. Some species can look unremarkable and be in the shop for months, as juveniles, but then suddenly when they start showing signs of becoming adults, or if they actually pair up and start showing signs of breeding, their colors often pop out like beautiful flowers in the spring. Some individual specimens, may also have been suppressed by more dominant fish and not dared to show their true colors, until the dominant fish in the same aquarium is sold. Those "blooming" fishes often get sold very fast to other customers, who happen to come to the aquarium store at the right time, when the fishes start showing their true value.

My personal opinion is better to choose not to breed extremely deformed unnatural strains that can't even swim, or see, properly, because I consider it to be cruelty to animals to deliberately raise such fishes. For instance, strains with extreme balloon eyes as big as their body, or extremely long veilformed multiple fins, or missing fins, that inhibits almost all the natural movements compared to a natural fish, or a nucalhump so big that it is a health hazard for the fish. Extremely shortened body (compressed back spine) is also very common, making the fishes look shorter, resembling balls. Everything to attract buyers, without concern for the longevity of the fish, or health problems that can arise. Please, do not contribute to this. The appearance and forced behavior of such strains are, usually, created in resemblance to waddling human infant toddlers, since that can trigger psychological parental instincts and emotions in humans. That makes the waggling fish seem "cute and adorable" and some people "babytalk" to the fish.

I realize there is a huge middle zone between extreme and no alteration, compared to natural forms. I do not really mind if you choose fishes with minor changes compared to wild forms, as long as the fishes can live "healthy" lives. There is a difference in the severity of the side effects, between a fish with only slightly shortened body and a fish with an extremely shortened body. Some breeding variants and hybrids might be fully capable of living a good life, if cared for appropriately in aquariums, while others are ridden with disability, ailments and dysfunction. Sometimes, it is difficult to draw a clear line, since "dignity" and "respect", or "compassion" are also concepts related to human emotions. Depending on your point of view, it might not always be appropriate to apply these human concepts directly to fishes.

If a hybrid fish is designed with a pouting "smiling" mouth that it cannot close, making it look "cute and adorable" and also inhibits some of their natural biting behavior, so that they are less armed for combat, is that a good thing or a bad thing for this fish in an aquarium? It depends on your point of view. The fish might not be fit to survive in the wild, but since it is meant to live only in captivity, in the artificial environment of an aquarium, with humans taking care of the fish, does it matter? This is a controversial topic and when discussing this, it usually ends up also involving related topics that are also controversial, such as fishes with artificial tattoos, cosmetic surgery, or genetically modified GloFish etc.

I personally think it is important to, preferably, choose breeding stock without serious genetic defects, so that the species does not degenerate. Genetic errors can be transferred to the offspring. However, if the fish has, for example, defects from old healed physical injuries, unrelated to its genetics, it usually, does not disqualify the fish for breeding purposes.

Try to avoid using any fish in bad condition for spawning, unless you have reason to prioritize future generations of the fish higher than the health of the parent.

When it comes to the breeding itself, you generally shouldn't disturb the fishes in the aquarium. Naturally, different species are varied in their sensitivity to this. Many species don't mind if you watch, maybe you can even take pictures without a problem, while some other species may need covering of the walls of the aquarium, to not get disturbed. ;-)

It is, usually, advisable to catch and remove parents of egg-eating and egg-scattering species directly after they have finished spawning. If you use a filter in the aquarium, make sure that no eggs have been sucked into the filter during spawning.

The hatching time of the eggs vary, depending on the species of fish and the temperature of the water. It is, usually, about 18 to 72 hours, but some eggs may take a lot longer. Eggs of some killifishes can be stored for many months.

Do you want to breed fishes that exhibits parental care, or want tips on plants suitable for breeding fishes, or water for breeding fishes, or inspiration on how to trigger spawning by imitating conditions in nature? If so, I suggest reading some of my other aquaristic articles.

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E-mail Max Strandberg