How To Increase Breeding Of Oscar Fish In Aquarium ~ Breeding Oscar fish (Astronotus ocellatus) in an aquarium can be challenging because of their large size, territorial nature, and aggressive behavior during the spawning season. Fortunately, it’s possible by providing them with the right spawning conditions and the proper care for their fry.

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Acquire a Breeding Pair

The chance of successful breeding of Oscars increases with buying a proven breeding pair from the pet store. Yes, a breeding pair is expensive, but it’s more convenient since there’s less waiting time involved. Take note that Oscars reach maturity when they are about 14 months old, while many mature Oscars will not spawn until they are at least 24 months old.

But if you’re willing to wait, you can get six young Oscars, place them in a single aquarium and allow them to form their pairs.

Once two Oscars have become a pair, they should be removed from the aquarium and placed in a separate tank. Breeding Oscars can become aggressive against other fish because of their highly territorial nature; otherwise, they likely will not spawn as well as expected.

Ensure the Right Tank Conditions

Keep in mind that Oscars are large fish, with many of them growing to a length of six inches. The spawning tank must then be large enough to accommodate the breeding pair and give them ample room. We suggest a 70-gallon, a 90-gallon, or a 125-gallon tank depending on the actual size of your breeding pair.

Remember, too, that a separate tank will likely be needed if the fry will be hatched and raised separately from their parents. In this case, a 55-gallon tank will suffice.

The tank should also have a glass cover with a heavyweight, such as a brick or a potted plant, to protect the Oscars. The tank’s overhead light should also have protection against water splashes.

Other Crucial Tank Conditions Are:

  • The filtration system should be sufficient to handle the enormous waste produced by the breeding pair during the spawning season. An under gravel filter combined with a large canister filter and trickle filters is a good start. 
  • Increase the water temperature to between 82°F and 85°F. Large heaters (i.e., not less than five watts) are needed for this purpose; be sure to protect the heaters from attacks by Oscars (e.g., use adhesive tabs, PVC tubes or sponge rubber).
  • Use either soft acidic water or hard alkaline water in the tank. Oscars are native to Central America, where their natural habitats are either of these water types.
  • Change the water partially – no more than 25 to 25% at a time – once a week or twice a week since even the multiple filters are unable to take the load.
  • Provide the breeding pair with plenty of durable hiding places. Skip the plants since these will not last – place large rocks, large-diameter PVC pipe, and clay flowerpots in the tank instead. The tank bottom should also have a large, wide flat rock about 8-12 inches in diameter.

Feed Them The Right Food

Oscars are more likely to breed when they are fed with an enriched diet. Otherwise, the breeding pair will produce weak eggs or fry that will eventually die no matter the corrective measures.

Be sure to feed the breeding pair with pelleted fish food, a staple in their diet, as well as invertebrates (e.g., edible food shrimp, earthworms, and aquarium snail), whole small fish, live crickets, adult brine shrimp, trout chow, and even thawed beef heart.


With these right conditions, the Oscars will likely begin spawning. You will see it when they start side-by-side wagging, gill flaring, and tail-slapping, among other behaviors. 

How To Increase Breeding Of Oscar Fish In Aquarium

You may also read How To Set Up An Oscar Tank Kindle Edition for more details on the matter.