Fishbowl Adviser

How Do Fish Mate: Everything You Need to Know

Just like all other living things, fish reproduce for their survival to ensure they aren’t extinct. But how do fish mate exactly?

Fish mate

How Do Fish Mate Actually?

Not all fishes are the same, and there are many differences between their species in the way they mate. It may be difficult to know when a goldfish is pregnant, but you’ll need to learn how exactly fish can reproduce to be prepared for it when it happens. Fish do possess specific reproductive organs that allow them to reproduce and make babies. As for how fish reproduce, you will find several types of mating processes:

  • Live-bearing
  • Egg-laying
  • Unisexual
  • Hermaphrodites
  • Broadcast Spawners


With live-bearing, the male fish will transmit sperm into the female using the anal fin, and the released sperm will fertilize the eggs that are stored in the oviduct of the female. After this happens, a fully formed fry that is ready for life will be born in a few weeks (approximately 3-4).

Female fishes that have gone through the mating process won’t necessarily have to copulate again to give birth. Some of them are actually known for reproducing every month, with the presence of a male fish.

Livebearers also usually have well-developed young compared to other fish species. Some of the most common livebearing fish are platies, guppies, mollies, swordtails, goodeids, cichlids, and seahorses, as well as stingrays, and many sharks.


Egg-laying is the process where the female fish will lay eggs that are going to be fertilized by the male fish. The fertilization will happen externally – oviparity as it is known in the biological world. The fertilized eggs will be placed in nests around different hiding spots close to the substrate.

However, different fish species will have different manners of laying their eggs. Betta fish, along with croaking gourami and paradise fish, will build bubble nests where the fertilized eggs will be kept before they hatch.

There are also egg scatterers who will litter the surrounding environment with their eggs. The eggs that are laid will eventually be fertilized by the male fish that will usually follow the female during the egg-laying process. These egg scatterers are barbs, tetras, danios, rainbow fish, and many others. However, even though the parents do not give any protection to their young ones, they will also be more likely to feast on their brood. Because of this, aquarists should keep the parents in a separate tank when the eggs begin to hatch.


Some fish species can reproduce just by themselves, without any help from a partner. These fish are all females and they will only give birth to females. These species do not need the presence of a male fish to reproduce. And since there is no need for males and their sperm, this form of reproduction is not mating but it still counts as a reproduction process.


There are also fish species that are hermaphroditic. These fish have both female and male sex organs in one body. Some will exhibit their attributes right from the cradle and stay like that during their entire life, while others will cross-fertilize to reproduce their young ones.

Among these fish species, you can find two types of hermaphrodites. The first being male and female fish who have chosen their type and who will reproduce and lay eggs. However, they can change their sexuality at any time. One fish can be born as a male and change to become a female in just a few years. This type is called sequential hermaphroditism.

If the male switches to a female, then the process is called protandry, and if a female changes into a male, the process is called protogyny. But with these, every fish will need a partner to mate and spawn eggs.

The other type of hermaphroditism is simultaneous hermaphroditism where the same species will have both male and female sex organs and reproduce by itself. When self-fertilization happens, the eggs will remain in the body of the fish until they are ready to be hatched and emerge on their own. The adult fish will protect their young until they are big enough to take care of themselves.

Broadcast Spawners

Broadcast spawners are fish species that reproduce by chance. The females will release their eggs while the males release their sperm in the water. They won’t directly release it on the eggs, but just in the water and wait for things to happen. Both the males and females will wait for fertilization to happen by chance. However, because it happens by chance, not all of the eggs will be fertilized by the male sperm.

Because the parents are not around to protect the fish from any danger, the young fish that will come from this type of breeding is resilient, strong, well-adapted, and able to survive from the first second.

Discus fish


When keeping the fish in a tank, it’s important to acclimate new fish to the tank, but it’s also essential to be prepared for their mating process. And you need to carefully observe the behavior of your fish. If you see betta fish fight, you might find the answer in their gender.

When you get a fish, you’ll need to know their gender and species (as well as the way they reproduce) so you know what to expect and how to reach. And you’ll need to make sure you do proper aquarium maintenance so you have a healthy environment for new fish.


  1. Reproduction in Fishes – PetMD
  2. How Do Fish Reproduce? – IMET
  3. How Aquarium Fish Mate – Cuteness


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