Intro to Breeding Freshwater Fish

Breeding fish can be fun, challenging, and sometimes frustrating.  If you have a male and a female of the same species, there is a chance you will get into breeding without even trying (especially if you have livebearers).  While other species you can create absolutely perfect conditions and nothing will ever come of it.

Types of Breeding

Fish breed though 2 main methods.  The first is the group with a majority of fish.  These are the egg layers who lay eggs and they are fertilized externally.  The second type is livebearers who fertilize internally and birth live fish.

Egg Layers

Within the egg layers, there are several methods females have for laying their eggs.  Depending on evolutionary factors, there are a few different methods varying from scattering eggs seemingly at random to holding eggs within their mouths to building nests.


Mouthbrooders breed with the female laying eggs and one of the parents takes the eggs into their mouth for the until the fry are hatched. In the wild, this serves to help protect the eggs from predators and from currents which can carry eggs away.  Some mouthbrooders are also good parents, looking after their young until they are old enough to fend for themselves. Some common mouthbrooders include some gouramis (anabantoids), many cichlids, and some catfish.

Bubble Nesters

Bubble Nesters breed by the male building a nest.  He blows bubbles and arranges them into a nest where the female lays her eggs.  Once the eggs are laid, the male guards them until they hatch. One common bubble nester is the betta.

By ZooFari [CC BY 3.0]
By ZooFari [CC BY 3.0]

Egg Scatterers

Egg scatterers breed with the female laying a large amount of eggs scattered all over the place.  Due to the large number of eggs and the randomness of where they end up, statistically some fry will hatch and survive to adulthood.  Rasboras, barbs, danios, tetras and some catfish are all considered egg scatterers.

Egg Depositors

Egg depositors breed with the male and female working together to find a suitable place to lay their eggs.  They typically search for a location which provides some cover like under leaves and rocks.  After the eggs are laid, the parents typically stay in the area to chase off any fish that might be coming in to snack on their eggs.  Some cichlids, including angelfish, discus, and some catfish are egg depositors

Egg Burying

Egg buriers are usually native to small pools that dry up during the region’s dry season.  During the wet season, they will bury their eggs in the mud.  When the pools dry up, the eggs will remain buried and safe until the rainy season returns.  Most killifish are egg buriers.


Livebearers take very little encouragement to breed.  If you have a male and a female together, there is a good chance they will reproduce. You simply need to provide a good environment and make sure you water parameters are in check.  Turning up the temperature a few degrees can help encourage breeding. Examples of livebearers are mollies, swordtails, guppies, and platies.

The biggest challenge with breeding livebearers is keeping the fry alive.  There is a very real possibility that your livebearers have reproduced before and you never noticed simply because the fry were quickly eaten by other tankmates.  This is a particular concern if you have fish that are a good bit bigger than your livebearers, e.g. angelfish, gourami, etc.

A pregnant female can usually be identified by their large, swollen stomachs.  If you are able to recognize when the female is pregnant, you can transfer her to a breeder box.  Breeder boxes should be reasonably sized.  Smaller breeding boxes can make the female uncomfortable and confined.  Also, females should be transferred to their breeder boxes several days before they give birth.  The sudden change in scenery and environment directly before birth can cause panic and result in the female aborting her pregnancy.

The Fry

So you’ve managed to successfully breed and have a school of fry to look after.  The easiest way to do this is to have a small separate tank for nothing else but the fry.  You can also use a hang on nursery which can often double as a breeding box. Fry are small and lack mobility.  They can’t handle a tank with a lot of current so you must be careful with your filter.  A hang-on filter is often too much for the fry.

Young fish need to be fed several times a day (up to 5 times a day).  Also, the food must be crushed up small enough to fit in their mouths. A variety of food can help fry grow quicker and healthier.

By Silke Baron [CC BY 2.0]
By Silke Baron [CC BY 2.0]

Best Fish to Get Started Breeding

Livebearers are by far the best fish to get started breeding as breeding them takes very little effort.  Mollies, swordtails, guppies, and platies are all perfect starting fish.  Make sure you have at least one male and one female.

A Word of Caution

Before you begin breeding fish, make sure you have a plan for what to you with them.  If you are going to sell them, give them away, start a second tank, or even use them as feeder for larger fish, that’s great.  As long as you have a plan.  If your tank is nearing its capacity, a few small fry won’t impact much.  But these will eventually grow into full size fish with a full sized fish bioload.  Overcrowding is a real concern here.