You will have the best chances if you find a proven breeding pair of oscar fish in a pet shop at a good price. The tubes are only apparent just before spawning. The male’s breeding tube is about a third the mass of the female’s tube, very thin, curved and comes to a point its length is far greater than its width. In the female, the tube (ovipositor) is short, stubby and flat at the tip as though sliced off, and about as long as it is wide. The only certain way to sex oscar fish is by looking at the breeding tubes. Many mature oscars refuse to spawn until they are 2 or even 3 years old. Size is not reliable, and even age cannot be counted on for getting results. Oscar fish reach sexual maturity at about 14 months when they are 6 to 10 inches long. So, if you find adults at the store, how do you pick out fish that are a possible breeding pair? Oscar fish are often brought back to the fish store after the 1-inch juvenile they purchased grew too big for their aquariums or bullied the other fish in the aquarium. If you don’t have large adults, you may be able to find some at your local fish store. If you’ve been keeping oscars a long time, odds are pretty good that you’ve raised a breeding pair. It’s a thrill when oscar fish breed for the first time. Make sure you have a breeding pair of oscar fish adults, and then you can move on from there.
It is a lot of work but is well worth it. If you keep the oscar fish ( Astronotus ocellatus), you probably know that it is a large cichlid that is not for every aquarist. Oscars do often breed in the home fish aquarium - and if you’re ready for this step, you can follow some basic instructions to breed them and raise the oscar fry successfully.