How to Tell the Difference Between Male and Female Oscar Fish

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How to Tell the Difference Between Male & Female Oscar Fish
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When it comes to fish that help create a dramatic aquarium setting, few fish are more exciting than Oscars. These fish are large, making an impact in the aquarium, and they have a lot of personality and can even learn to enjoy being petted.


Oscar fish are of a type known as monomorphic fish, meaning that the male and female look exactly the same. According to, it is impossible to tell Oscar fish sex from a cursory physical examination in the tank because they are the same in size, shape, and color. Also, you will not be able to tell Oscar fish sex while the fish are babies. Determining the sex of an Oscar fish takes time and patience. The Oscar fish male and female difference can only be determined when the fish are at a minimum of one year old.


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Male and female Oscar fish

Fishxperts says that Oscars live for 10 to 13 years. After 12 to 15 months of age, Oscars have grown to be about 4 to 5 inches long. At this stage, an inspection of their reproductive area can reveal Oscar fish sex. Each of them have a different set of genital features which can be determined by close observation of the anal area. Both have two holes. One is the anus and the other is the reproductive organ. In males, the sexual organ forms a small spike. In females, the organ is wider and more blunt because it is the tube where the eggs are released.


Oscar fish breeding signs

If you are fortunate to have young Oscars, you may be able to observe them as they grow and first start to mate, and this can give you a precise knowledge of which fish is male and which is female. When Oscars are ready to reproduce, the female will swim around in a circle with her belly almost touching the surface where she will lay her eggs. This is often a flat rock or other surface in the tank. One of the Oscar fish breeding signs is that she may clean the surface of the rock with her mouth in preparation for the breeding ritual.


During this time, the male Oscar will be following closely behind the female depositing his semen, also known as milt, over the eggs. says that females will lay eggs whether there is a male in the tank or not. If you have two Oscars in your tank and one lays eggs but the other does not seem interested in continuing the mating by fertilizing the eggs, then it is likely that you have two females.


Oscar fry will hatch within 72 hours of being fertilized. Sometimes Oscars will eat their eggs. If you want to maximize the chances of your Oscar fry hatching, consider moving the parent fish into another tank while the Oscar fry grows.

Oscar venting

The process that can help you determine the difference between male and female Oscars is called venting. Quebec Cichlides (Oscars belong to a group of fish called cichlids) describes the first step in the process of fish venting as capturing the fish in a net. While keeping it in the water, flip the fish over and take it out just enough to see the genitals. Observe the holes and the size, shape, and color of each.


In females, one hole will be bigger than the other. The bigger hole is the egg tube. In males, the two holes are the same size. The coloration around the genitals will also likely be different in males and females. The female's skin will be lighter than the male's skin. Handle the fish very gently while doing this so you do not cause harm or stress to the delicate fish.



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