Breeding Oscars is a challenging activity that should not be entered into by the faint of heart. Before you make a decision to jump into breeding, you should ask yourself the following:
What are you going to do with the fry?
Oscars can produce close to 2000 fry per batch. Once they get going, they produce a new batch about every month or so. You can use six 55 gallon tanks to raise 500 fry to a sellable size. This means that he was culling nearly 1500 fry out of each batch, and that assumes that a batch could be raised to sellable size before another batch was ready to take its place. To raise a full batch to sellable size, you would need the equivalent of twenty four 55 gallon tanks. How long would your local market be able to absorb this number of new fry of one color type of oscar before it became dramatically devalued? You can always look to markets outside your immediate area, but that involves shipping, which is expensive and time-consuming.
Can you house the parents comfortably?
For a breeding pair of oscars, you will need at least a 75 gallon tank with nothing else in it. Anything else is a risk to the eggs and/or fry, and will most likely get beat up badly by the expectant parents.
How will you get a mated pair?
This is harder than you might think. Sexing oscars is impossible without cutting them open or watching them breeding. This means that it is difficult just to make sure that you have a male and a female. Even if you have a male and a female, there is no guarantee that they will like each other well enough to mate. Oscars are at least as picky as humans when it comes to selecting a mate. Many people who are determined to breed oscars buy several (5 or more juveniles) and raise them in the same tank together until a pair or pairs form. This can work in theory, but there is no guarantee you have a mated pair until you actually have a batch of fertilized eggs. Remember that they will not actually start mating until they are at least 7 inches. This means that the grow-out tank for your potential parents will need to be able to accomodate 5 or more somewhat agressive, very messy fish of 7 to 9 inches. A 180 gallon or larger tank will be necessary for this.
Often times, 2 females will pair up, go through all of the motions, and actually lay eggs. The only problem is that the eggs are not fertilized.
If you have satisfactorily answered all of the above questions, and have a mated pair, you are ready to jump in.
You will need a 75 gallon or larger tank for your breeding oscars. This tank should be well filtered, and well maintained, just like any oscar tank. Substrate should be either sand, or gravel of pea size or less. Decorations can include driftwood, and large chemically inert rocks. There should be at least one good-sized piece of slate or other flat rock in the tank. Lay this flat on top of the substrate in a protcted area of the tank. Under normal circumstances, keep the temperature around 78ºF. When your oscars start to display mating rituals, you can encourage them by doing a large (70% plus) water change, and increasing the water temp (slowly) to about 84ºF. This simulates the influx of warm spring rains that would occur in their native rivers. Lighting should be subdued. A blackwater environment with about 40 watts of daytime lighting would be ideal.
The Mating Ritual
When a pair of oscars is preparing to mate, several things will occur. These include moving gravel (or sand) around in the tank, rubbing on slate (or other flat rocks) in the aquarium (this is called “cleaning the slate”), lip locking, and shimmying up next to each other. When they are getting ready to actually lay/fertilize the eggs, they will start spenging more time right around the slate or other area where they plan to place the eggs. When the breeding tubes drop, they are getting ready to do the deed. This is also a good time to try to sex your oscars. The male will have a smaller, pointed breeding tube, and the female will have a larger, breeding tube with a rounded end. When the eggs start coming, the female will also obviously be the one depositing the eggs.
From the beginning signs of mating ritual, to actual laying of eggs, it may be several hours, or it may be several weeks. Other than the water change and temperature increase, there is not much you can do to hurry them along. Also, it is quite possible that they will not get it right the first time (or second, or third . . .). Often, hopeful parents just dont know exactly how to do it. Sometimes they lay the eggs in the wrong spot, sometimes they eat the eggs, sometimes they dont get the eggs fertilized, etc. Just give them some peace and quiet, and let nature take its course. Patience is a virtue.
When the eggs finally arrive, there will be quite a batch. If they are fertilized, they will turn amber (yellow) within a short period of time. If they are not fertilized, they will remain and off-white color. If your eggs are not fertilized, it does not necessarily mean that you have two females, but it is an indication that this may be the case. Young oscars have to learn how to do everything, and they may not get it right at first. If you have a few batches of eggs that all turn out to be unfertilized, then you almost certainly have two females. Regardless, the parents will hover in and around the area of the eggs to protect them.
Some breeders will recommend removing the slate with the eggs on it from the tank as soon as they are laid and prove to be fertilized. This is in hopes of maximizing fry survival. However, IMO, that eliminates much of the joy of wathcing Oscars raise their fry. They are great parents once they get the hang of it, and the fry will hover close to the protection of the parent whenever they sense danger.
After a few days, fertilized eggs will hatch. At this stage, the fry will be attached through the egg-sack to the slate. At this point, they cannot swim freely and are called “wigglers”.
Care and Feeding of Fry
Note: From here on, the discussion is based on reading of other’s experiences, and my knowledge of raising other types of fry. My oscars laid eggs once, and they were promptly eaten by the pleco. During the mating process, one of my oscars (the male) dislocated his jaw during some serious liplocking. Since then, the female has pretty much ignored him, and they have not mated since. If anyone with real experience raising fry wants to chime in and correct any errors and/or provide additional information, it would be greatly apreciated.
Once the wigglers detach themselves from the slate, they are officially fry. Very hungry fry. There are many ways to feed fry. Some people suggest setting up a brine shrimp hatchery, and trying to time the hatch of the brine shrimp with the time the fry will be free swimming. Another possibility is grinding up flakes between your fingers and thumb. Hikari makes “baby” sized cichlid pellets, but I doubt oscar fry would be able to eat them at first. All I can say is try it and see. Regardless, you will need a food that is small enough to fit in their mouths, and that will provide them with adequate nutrition to grow.
When the parents show signs of mating again, it is time to remove the fry from the tank. If they are still present when the eggs are laid, they will be perceived as a threat to the new eggs and will be eaten.