How to Tell the Sex of an Angelfish

Observing Spawning Tubes

Wait until the angelfish are mature. In order for angelfish to become mature and be able to mate, they need to be properly cared for and given adequate space. If they are cared for and given the right amount of space, they may reach maturity as early as 5 to 7 months of age. At this time, they will be mature enough to breed and spawn. Adequate space would be about 7-10 gallons of water per angelfish. Sometimes, though, even with the best care and the right amount of space, certain strains of angelfish might take longer to mature.

Observe the tubes that come down from their undersides. Once the angelfish are mature, you will notice that small tube-like appendages have emerged on their bellies. These tubes will be just behind the “feeler” fins on their bellies. You might notice them more if other fish in the tank are breeding. These tubes are very small, so you will need to look closely to notice them. Catching the fish in a net or putting them in a smaller tank temporarily for observation purposes might help you get a better look, just make sure you handle the fish carefully.

Determine the sex based on the shape of the tubes. Once you’ve located the tube and can examine it adequately, look at the shape of the tube. On male angelfish, the tube will be pointy and narrow. It might look something like the tip of a sharpened pencil. With female angelfish, the tube will be rounder and have a cylindrical shape. If you happen to have another breeding pair, you can put the angelfish you want to sex in with them. This might encourage them to drop their tubes for you to be able to tell their sex.

Examining Body Shape

Look for a large crowned head on male angelfish. On a male, the front of their heads will have a high, noticeable crown. It will likely look much more prominent and a bit larger than the female angelfish. This feature might be more prominent at maturity, but you may be able to notice it earlier on in the lifespan, as well. This isn’t a sure-fire way to tell the difference between the sexes. In some strains of angelfish, this physical difference might not always be present.

Check for a smaller, more rounded shape on female angelfish. Female angelfish might have more rounded bodies than males. Female angelfish are also generally a little smaller than male angelfish. If you want to buy pairs to breed, try buying a few smaller angelfish and a few larger angelfish. Once they’re mature, you’ll more than likely find out you have a few males and a few females. On female angelfish, the line from their dorsal fin to their eyes also tends to be a bit straighter than that of the male’s.

Watch them as they swim towards you. Sometimes with female angelfish, you might be able to notice a difference when they swim towards you. The shape of their bellies might be a bit bigger or wider than male angelfish. Try looking into the tank and waiting for each of the fish to swim towards the glass. Observe the shape of their bellies from that angle.

Watching Mating Groups

Put a group of about 4-6 angelfish together. When purchasing your first set of angelfish, consider buying 4-6 different juvenile fish and putting them together in a tank. Make sure the tank has adequate space for all the fish. When selecting your fish, consider picking a few fish that are on the smaller side, and a few that are a little larger. This might increase your chances of them being different sexes and eventually pairing to spawn.

Watch their spawning habits. Once the fish are mature—usually once they are between 6 and 12 months old—they will pair off to spawn. At this time, start keeping a close eye on them to see their behaviors. Not only will you be more likely to see their spawning tubes at that point, but you will be able to see which fish pair off to spawn together. Observe these behaviors carefully, though—sometimes fish of the same sex will try to spawn, unsuccessfully of course. Sometimes spawning pairs of angelfish will “kiss” or lock lips. Sometimes this lip locking can be quick and cute, or even a little aggressive, with the fish chasing one another around the tank.

Determine which angelfish are male and female based on pairings. Once your fish have paired to spawn, you should be able to determine which fish are female and which are male based on their pairings. This might not be the most efficient way to tell the sex of an angelfish, but since the sexing of angelfish is an imprecise process, it’s one of the most accurate. You may actually observe a female angelfish laying her eggs with careful observation. Keep in mind, though, that even some of the most experienced angelfish breeders and keepers have trouble distinguishing between the sexes.