So, you know how there are mommy fishes and daddy fishes, right? Well, they like each other very much and when they are ready to make babies, they get very close to each other.
Daddy fish then releases something called "sperm" into the water. This is like tiny little seeds that can fertilize mommy fish's eggs. Mommy fish then releases her eggs into the water too, and if daddy's sperm finds them, they can stick together and make baby fish.
Sometimes, mommy and daddy fish both lay their eggs and sperm in a hole in the ground or in a nest that they build together. They take turns guarding the eggs until they hatch and become baby fish.
It's very important for fish to make babies because that's how they keep their population healthy and growing. And just like how people take care of their babies, fish take care of theirs too by making sure they have enough food to eat and by protecting them from danger.