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How To Prevent Aquarium Fish From Breeding?

Many aquarists love to breed fish in their aquariums, which is undoubtedly a fun task that develops many skills related to the hobby. However, most aquarists don’t want to breed aquarium fish.

In this article I will discuss how to prevent aquarium fish from breeding.

So without further ado, let’s get into it.

How to Prevent Aquarium Fish From Breeding?

how to prevent aquarium fish from breeding
You designed and set up your beautiful aquarium, waited for it to cycle, introduced the fish, and went to all the trouble for it to be perfectly balanced. Until, during an inspection, you notice several fingerlings in the tank, and the next day more fingerlings; this goes on until you end up with an aquarium full of fish and a big problem.

This is common, especially among younger aquarists with small to medium-sized tanks with livebearer fish, which breed quickly.

Luckily, there are some steps you can take to prevent (or at least minimize) this issue from occurring.

Listed below are the best techniques to avoid the number of times your fish breed. These tips will certainly work for some species, and the fry will no longer be a problem.

These techniques will only minimize the amount of fry produced for extremely prolific fish, which already helps a lot.

Keep only one sex

The simplest way to ensure that fish never breed is only to keep single-sex fish in your tank.
To reproduce, most ornamental fish need a male and a female. To ensure that fry will not appear, it is ideal for keeping only male fish.

In addition to being able to buy a female already pregnant unintentionally, some females are known to store the sperm of the male fish, so they can breed for months even when they are kept isolated.

Although it seems simple, this technique brings some complications. Not all fish are easy to sex correctly. When buying your fish, ask the seller for help; he will be able to help you.

The second point is the highly territorial and aggressive behavior between males of the same species. This aggressiveness varies depending on the species and can be resolved and mitigated in several ways.

Look for our articles on the species you want to keep; we talk about it in each species guide!

Keep species that are oviparous

Oviparous fish species specialize in reproducing only in some favorable environmental conditions, along with the egg development time, making the process even more difficult.

We can mention the Tetras, Danios, Rasboras, Bettas, Barbs, and Cichlids among these fish.
Even if everything in your tank is up to date, probably in a community tank, the eggs will be eaten. Even the parents themselves can end up eating eggs and fry.

On the other hand, fish that give birth to already formed young, swimming freely and feeding, are incredibly prolific and have a higher survival rate.

Avoid keeping viviparous fish like Molly, Guppy, Swordtail, and Platy if you don’t want fry in your tank endlessly.

Keep specialized species or fish that breed in extremes

Mainly among the oviparous, we have some fish that need conditions that we can consider extreme in an aquarium.

An example of this is the Cardinal Tetra, which can be safely kept in a typical tropical community aquarium but will only breed in very soft water with a pH close to 4.

Species like the Bumblebee Goby need a specific salinity to trigger breeding mode.

Some fish, like some Killifish, lay their eggs in the substrate, and these need to dry out to complete development.

Choosing these types of fish with characteristics so necessary to reproduce is undoubtedly a safe way out for those who do not intend to find fry in their tanks.

Any aquarist can easily find a number of these species in different physical and online fish stores.

Keep different species

Some species do not live on shoals and are solitary. Using different fish of this type, you can populate an aquarium with the certainty that no new fish will appear.

Because they are different species, they will not reproduce. But be aware that some species can generate hybrids. Read our articles and learn which ones you can’t mix.

Control reproduction by manipulating the environment

Most people know that most fish need specific and favorable conditions to reproduce. This is the crucial point of birth control measures.

These measures often manipulate environmental conditions, making the environment unsuitable for reproduction.

Control the feeding rate

This technique works best with viviparous fish. It is one of the easiest ways to decrease the reproduction rate of these fish.

Most livebearers will reproduce lower if they don’t have plenty of food.

In addition, as they are voracious animals, they will tirelessly seek food in the aquarium, which will make them control the fry population themselves.

Another alternative is to reduce the supply of live and fresh foods, proven to help trigger ornamental fish breeding.

Change your tank’s conditions

As mentioned earlier, fish need specific conditions to reproduce. A great way to control fish reproduction is by manipulating tank conditions.

Fish will simply avoid breeding when kept outside that range of parameters suitable to support reproduction.

Commonly used techniques are lowering the temperature and modifying the pH.

Keep in mind that keeping your aquarium at unfavorable parameters for fish can slow or accelerate the development of the animals and make them susceptible to diseases.

Never subject your animals to irregular parameters. Just keep out of the ideal for reproduction.

To make these changes, you need to know the ideal conditions for fish to breed. Keep your tank in a perfect situation where the fish can live healthily but not reproduce.

Why prevent aquarium fish from breeding?

how to prevent aquarium fish from breeding
In addition to the issue of personal taste, of you just not wanting to breed your fish, we can cite numerous reasons to prevent your fish from breeding.

The main thing is the disruption of the general balance of the aquarium; everything in the tank has to be balanced, including the amount of fauna. As healthy and fun as an aquarium with lots of fish may seem, it’s cruel.

Overcrowding goes against animal welfare rules. The super population is a big problem when dealing with some fish species that breed uncontrollably, like Guppies and Mollies.

In addition to the lack of physical space, which prevents fish from forming their territories, many fish will generate an organic load far above what the filter can handle. This is the disaster equation, which will result in a disease outbreak and the total crash of your system.

Due to poor water quality, algae growth may increase, leading to outbreaks.

Because of all those facts, overpopulation forces the tank tutor to intensify the number of weekly maintenance and water changes in the aquarium in question.

To generate this organic load, you will have to feed the developing fish, which means a considerable increase in the amount of feed to be purchased, thus increasing maintenance costs.

Each species of fish has its way and speed of eating. When you have a lot of fish in the aquarium, some will certainly not receive adequate food and will end up malnourished.

This is certainly the problem with many aquarists who struggle with the uncontrolled reproduction of their fish.

How To Dealing With Undesirable Fish?

Even if you follow our teachings at risk, some fish are highly prolific and will reproduce anyway. If this is your case, you can take a few steps when dealing with unwanted fish from your tank.

Natural selection (law of the strongest)

It’s one of the most natural and easiest ways to give yourself unwanted fry. Baby fish are defenseless to all types of predators, making them easy prey.

By decreasing the number of hiding places and establishing more open decorations and fewer plants, the fry is even more unprotected. So we encourage bigger fish to eat them.

Using species with piscivorous habits such as Gouramis or Dwarf Cichlids also helps control the fry population.

Removal and destination

If you are thinking of getting rid of the excess fish in your tank, the correct thing is to use it for some purpose.

Donating fish is often the easiest option. There are several aquarists out there willing to adopt your fish.

The same way you bought your fish, others want it too. Furthermore, raising ornamental fish can be a highly profitable activity, so why not oversell your fingerlings?

Some fish stores regularly buy fish from their customer. Others accept it as a bargaining chip for products, plants, and other animals.

Never release your fish into the wild. Many aquarium species are not native. When released into lakes, ponds, rivers, and streams, they can cause serious problems, such as transmitting diseases, competing for food, harming, and even causing the extinction of native species.


If you suffer from this problem of unwanted reproduction in your aquarium, then this guide will solve your problems. But remember, even after everything, some fish will continue to reproduce, even on a smaller scale.

Make sure you use the possibility of manipulating the water parameters to your advantage and choose the best fish alternatives for your project.

Before acquiring new fish, read our articles about the chosen species.

Finally, be aware of the dangers of releasing them into the wild. In situations like this, donating or selling the animals to other aquarists, stores or schools is the best alternative.