Flowerhorn HobbyThe luohan, explained

Tools

Male or female checker

The usual signs, weighted by how much they are actually worth.

Check your fish

Most sexing advice throws every sign at you as if they all count the same. They do not. The vent is worth more than the kok, the kok is worth more than the fins, and eggs settle the argument. Answer only what you can really see.

Male or female checker

Answer what you can actually see. Skip nothing, guess nothing.

What do you see

Vent shape (the breeding tube, between the anal fin and the belly)

This is the single most reliable clue on a mature fish, but it is hard to see on anything under four inches.

Black spots on the dorsal fin (the fin along the back)

Common on females of many strains, but far from universal. Some males keep juvenile spots, and some female lines have none.

Kok size compared to other fish the same size

Males usually grow the bigger kok, but a well-fed female can out-kok a poorly kept male.

Fin shape

Look at the dorsal and anal fin tips. Damage from fighting or shipping makes this one unreliable.

Body shape

Only useful when comparing fish of the same age and strain.

Size compared to tank mates or siblings from the same batch

Males often grow faster. Useless on a fish you bought alone.

Behavior you have actually seen

Laying eggs settles it. Everything else here is weak evidence, since both sexes dig and flare.

How big is the fish

Sexing gets much more reliable as the fish matures. Under three inches, almost nothing is dependable.

?Answer the questions above

    Why the signs are weighted this way

    • Eggs beat everything. A fish that lays eggs is female, full stop.
    • The vent is the best visual sign. On a mature fish, a thin pointed tube reads male and a wide blunt one reads female. It is also the hardest to see, so it is worth being patient for.
    • Dorsal spots lean female, and that is all. Plenty of males keep spots from their juvenile pattern, and several female lines have none.
    • Kok and fins are tendencies, not rules. Males usually grow larger koks and longer fin tips. A big female on good food will beat a neglected male on both.
    • Size only counts within one batch. Comparing your fish to a photo online tells you nothing.

    For the full walkthrough with a labeled diagram, read how to tell a male flowerhorn from a female. If you are sexing fish to pair them up, the breeding guide covers what happens next.

    Questions

    How accurate is this?

    It is as accurate as your answers. On a grown fish where you can see the vent clearly, it will usually be right. On a two inch juvenile, nobody is reliably right, including experienced breeders.

    My fish shows male signs and female signs. What now?

    That is normal on a young fish. Give it two or three months of good food and clean water, then look at the vent again. Individual fish also just break the pattern sometimes.

    Does a female flowerhorn get a kok?

    Yes, many do, especially well-fed adults. It is usually smaller than a male's of the same age and strain, but a kok on its own does not make a fish male.

    Can a fish lay eggs without a male?

    Yes. A lone female will often drop infertile eggs. It still confirms she is female.