My male Guppys won’t stop chasing the females, what can I do?

Guppys may look stunning, but they’re the worst-behaved fish going, and once they start breeding they never stop. Seriously a single female can repopulate an entire lake or stream, and no that’s not an exaggeration. A female guppy will give birth to up to 200 fry, although I’ve heard that number a lot, and sure I’ve had old huge females have way over 100 fry, but the reality is closer to about 30. But within a couple of months, those fry are ready to breed, so you will have about 15 females each having up to about 30 fry each every month, and then the second generation gets in on the act. No, you can’t sell these for a profit, or normally even sell them.

In aquarium-bred strains the males are complete sex pests, in the wild they’re completely different. The males are a lot smaller in comparison to the males, and the males will approach the females, perform a courtship dance of sorts, and wait for her to respond. If she swims off that’s it, at least for the next 10 minutes or so. I’m not saying he won’t try again to court her, but this frantic biting and chasing doesn’t happen to the same extent.

I often wonder is this because of potential hybridisation Guppys and Endlers are closely related, and it’s likely there is some Endler genetics in aquarium strain Guppys, and Endlers have different courtship, with some types having female lead courtship. Have we messed up these innate rituals, or are aquarium Guppys just more aggressive?

Either way you have an issue. If you want a mix of males and females, you will need at least 3 females to each male. Make sure there are plenty of places for the females to hide. Plants are idea for this, and make sure you have a plan for the fry. Most shops won’t take home-bred Guppys unless you are breeding for particular tail shapes or colours.

Otherwise just keep males alone, Yes they will chase each other, but that will be spread out amongst each other. Males don’t live as long, but females can hold sperm for at least 9 months, so will be having fry, with males in the mix for a while to come.