Breeding Oscars (Astronotus ocellatus)

Posted in About Oscars


It is the goal of many Oscar keepers to develop a breeding pair and to both observe their spawning behavior and raise the fry. This article provides some basics on how to identify breeding behavior, as well as providing some basic instructions on how to successfully rear the fry. It does not detail methods to develp a breeding pair.

Breeding Behavior

Oscars will lay their eggs on a flat surface in a single layer (no egg will be on top of another one). A flat rock like slate is ideal, or they have been known to clear the gravel and lay on the bare bottom of the tank. They will work for days picking up the gravel building mountains in the corners. Between ” digging ” they will go thru liplocking, shaking, quivering and sometimes aggression towards each other. Their color variances also intensify during this period. This is all normal but the twist of this is….The female may lay eggs regardless of whether there is another fish in the tank or not. It is also possible to have two females and have one or the other lay eggs. To further confuse things, two females may become aggressive towards each other while one, or the other, or both are laying eggs. To the the untrained, or even the trained eye, this sometimes looks like mating behavior between a male and female. The best thing to do if you are uncertain about whether you have a pair or not is to keep observing and asking questions on the Oscar Advice Forum.

Got Eggs?

Fertile eggs will be amber in color after 24 hours. White eggs are infertile. If the eggs are white, take the slate out or clean the tank. That is, if you can get them before your Oscars eat them.

Fertile eggs? Now it gets complicated !! Oscars are very good parents once they get some practice. New parents might raise the fry right away but unlikely. The eggs might be there lunch or they might let the eggs hatch to the wiggler stage and then eat them. OR if there is any other fish in the tank, they might just get a midnight snack. ( If there are any other fish in tank, take out ASAP ). If you think or know that you have a breeding pair and you want them to raise their fry, the best thing to do is keep them in a tank by themselves with no other fish (not even a pleco). If you wait until they have fertilized eggs to remove the other fish, you are likely to upset them enough so that they eat their eggs.

Leave the eggs with parents or take the slate out to hatch???

Big question. I have done both and I recommend letting the parents try. They teach the fry to come to the front of the tank for feedings and if the fry stray too far away they will suck them in to there mouths and place them in the “pits”.

If the parents keep eating the eggs or fry you can take the eggs out and hatch in a 10 gallon bare bottom tank. Make sure the tank is established and the water temp matches the parents tank. Use tank water in a bucket to make sure eggs are covered while moving them. Cover all the intakes with nylons or filter material. You don't want the fry to be sucked up into the filters. Sponge filters are excellent also. They pose no hazard to the babies at all, and they will eat the food that gets stuck to them.

Place the slate upright at the back of the tank and place an airstone in at the base to agitate the water in front of it. This will mimic the fanning that the parents do. Within a few days you might see a thickening or a fungus growing on top of the eggs. This thickens as the eggs hatch. You could use use product called Meythlene blue to prevent the spread of this ” fungus ” but I personally never had any problems.

After the eggs are laid, you should be able to see wigglers in the “fungus” within 2 to 3 days. Shut the tank lights off and use a flashlight to look around at different angles. If you don't see wigglers the eggs were not fertile, fungus killed them or they have moved off the slate into there hiding spot. There might be times that you think the fry are dead or have been eaten but they are in fact hiding in the gravel pits, underneath the gravel or behind the slate. Now is the time to start making brine shrimp. (see the Baby Brine Shrimp article submitted by me in the Freshwater Articles section)

Keeping it Clean

Water quality is of super importance. Do a 25% water change daily cleaning the bottom of the tank to remove all food residue. The best way is to use an airline to suck it out into a cup, bowl or pitcher. Then siphon the babies that you pick up back into the tank. It is almost impossible to clean the tank bottom without sucking up a few of the wigglers.

When you refill the tank, be sure that the water you put in is the same temp or maybe just a little warmer than the tank. Siphon it in with an airline slowly to minimize the effects of any variances in water temperature.

This article submitted by Julesgmp and MattR