About the Signs of Breeding in Oscar Fish

By Kevin Freeman

When Oscar fish are ready to breed, common signs and behaviors for the mating process can often confuse fish owners into thinking that a fight to the death is taking place. The Oscar fish is a sometimes aggressive breed; it is not uncommon to see quarrelsome behavior. However, there are certain behaviors to watch for that are sure signs of breeding rather than fighting. If you are raising or breeding Oscars, this knowledge is essential to avoid any misunderstandings.

The Facts

The Astronotus Oscellatus, also known as the Oscar, is an aggressive species of fish, even the nicest of which will be inclined to get into an occasional scuffle with his or her neighbors. Because the signs of breeding in Oscars are so similar to those of territorial fighting, it can sometimes be difficult to determine if your Oscars are ready to breed.

Risk Factors

Common breeding signs to look for in Oscars include lip locking between mates, frequent chasing of each other through the aquatic environment, shivering or shaking that is usually accompanied by tail lashing, and even nipping and biting that can result in the violent removal of strips of flesh. Mating Oscars have even been known to kill their partner on occasion during the violent mating ritual.

Expert Insight

When breeding Oscar fish, the recommended course of action is to allow six young Oscars to grow together in a shared environment. As they reach sexual maturity, the Oscars will select their mates from among the companions. Oscars can be picky when choosing their mates, so this process will often result in only one pair being formed. Because mating pairs can be overly territorial and aggressive, it is also advisable to remove any companions once a pair has formed.


Oscar fish tend to prefer large, flat pieces of stone to lay their eggs upon. Granite slabs are a popular choice for egg-laying stones among aquarists because they can provide a smooth, flat surface on which the female can lay her eggs. When such a stone has been chosen, the fish will often clean the stone's surface with his or her mouth in preparation for the laying of the eggs. This behavior is a good indication that the mating ritual is taking place.

Time Frame

The typical gestation period for Oscar fish eggs is typically three to 10 days, depending on water temperature. As a rule of thumb, the warmer an environment's water is, the faster the eggs will hatch. After the eggs have been laid, it is important to remove any other predators from the environment as they will consume the 1,000 to 3,000 eggs, as well as the resulting fry. The parents, however, are protective toward their young and will aggressively defend the tiny offspring.

Expert Insight

If you are considering breeding Oscar fish, be prepared for aggressive behavior or the death of your fish, a picky mating selection, the need for an isolated environment and a great deal of offspring when the young are hatched. Keep in mind through the process that the water temperature and pH level must be very carefully monitored both to ensure that the fish are healthy and happy and to promote the healing of any wounds that are caused by the process.