How To Stop Fish From Breeding ~ The best way to prevent fish from breeding is to ensure that the conditions in their tank aren’t conducive to mating. These conditions include the temperature, mineral, and pH balance of the water; the hiding and spawning places; and the type and amount of food provided to them, among others.

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Indeed, changing the tank conditions is crucial in stopping fish breeding, even when it has started. But be careful about doing so since there’s a thin line between stopping fish breeding and killing the fish.

Tip: Research about the optimum conditions for breeding regarding the fish in your tank – guppies can breed in nearly any situation, but Oscar fish require specific conditions.  Then, tweak these conditions, a trial-and-error method that will yield the desired results within a few tweaks. 

Change The Water Conditions

Aside from separating the male and female fish, changing the water conditions should be the first step. But don’t take drastic measures, such as lowering the water temperature by 10°C in one go, since these will agitate, if not harm, the fish within a day or two. Instead, decrease the water temperature little by little until the desired temperature to stop breeding is reached.

For example, discus and other related species usually start breeding when the water temperature ranges between 20°C and 31°C. The ideal light condition is moderate to low with a 6-7 pH level. You can stop them from breeding by decreasing the water temperature by 3°C-5°C over seven days or so; use the Capetsma Aquarium Thermometer to ensure accuracy. 

Think about changing the pH level and light conditions, too. But a lower water temperature usually does the trick since fish breed in near-ideal conditions – even a single aspect being off will stop breeding. 

Change The Food

Of course, feeding the fish with pelleted fish food and/or other staple food is still a must, as well as feeding the fish with the right amount and frequency for good health. But be sure to withhold different food types that encourage spawning, especially adding other food that results in an enriched diet.

For this reason, don’t feed fish with live foods like fruit flies, mosquito larvae, whole small fish, earthworms, live crickets, and aquarium snail. Don’t also feed sexually mature fish with adult brine shrimp and thawed beef heart, especially Oscar fish, since these make for an enriched diet. 

Change the Tank Environment

Many fish species breed in rainy season. Thus, it makes sense to change the tank environment to simulate the dry season’s conditions.

A few things to keep in mind: 

  • Keep the tank’s water level at its normal height. If you’re trying to simulate the rainy season, you will decrease the water level to half of its normal height and then add water every day – do the opposite. Remove the spray bar or drip system from the tank since these devices simulate storm conditions.
  • Remove the possible hiding and spawning places, including plants, flat stones, and tunnel structures in the tank. Otherwise, the fish will have more places in which to breed in private and hide their eggs.


As with encouraging fish to breed, stopping them from breeding can be a trial-and-error endeavor. Your basic knowledge and skills in fish care will be valuable in this regard.