Aquarium Fish Breeding Overview

The most rewarding and fascinating part of being a hobby aquarist is breeding your own tropical fish. The buzz that comes from successfully raising some baby fish (or more correctly, fry) is often the kick start for a lifetime’s passion for many people, and the thrill is one which never entirely disappears even after years of keeping and breeding all kinds of fish. One thing that makes aquarium fish breeding so interesting is the variety of different strategies that fish use for reproduction and the range of different behaviors that they adopt.

There are basically two main groups of breeders: livebearers and egg-layers. In livebearers the females are fertilized internally and live fry are then born, while the egg-layer’s eggs are fertilized after spawning and later hatch into fry. The majority of fish are egg-layers and these can be further divided into those which protect their eggs and young (parental species) and those which leave their eggs to their own destiny (non-parental). In fact some of these species may well dine on their eggs or fry shortly after spawning or giving birth! Some parental species tend to care for their young for a short period of time and then may also resort to cannibalism as well. They may also eat their young if they are disturbed or upset for any reason during this rather anxious time and can become quite territorial and aggressive while protecting their offspring.

There are many fascinating techniques that egg-layers use:
Egg-scatterers: These (non-parental) species simply scatter their eggs among plants or on the substrate.
Egg-depositors: deposit their eggs on a substrate (tank glass, wood, rocks, plants) and usually lay less eggs than egg-scatterers, but the eggs are larger. Some egg-depositors form pairs and have advanced brood care where the eggs are guarded and cleaned. The eggs take a few days to hatch, and the fry are also guarded by the parents. However some egg-depositors lay their eggs against a surface, where they are abandoned but these species do not usually eat their eggs.

Egg-buriers: bury the eggs in the substrate or hide them in safe crevices.

Mouth-brooders: Are species that carry their eggs or larvae in their mouth.
In some species (ovophiles) the female picks up the eggs immediately after laying. The male has spots on his anal fin which look like eggs and the female thinks these are eggs she has missed. She will try to pick the egg spots off the anal fin while the male releases sperm into the her mouth, and so fertilizes the eggs. The female will carry the fertilized eggs in her mouth until the fry have developed. This may vary from about 18 to 25 days.
Other species of mouth brooder (Larvophile)s lay their eggs on a substrate and guard them until the eggs hatch. After hatching, the female picks up the fry and keeps them in her mouth. When the fry can fend for themselves, they are released.

Nest-builders: Nest builders build some sort of nest for their eggs. The nest is usually in the form of bubble-nest formed with plant debris and saliva-coated bubbles (labyrinth fish, catfish), or a excavated pit in the substrate (cichlids). Nest builders practice brood care.

With such a fascinating range of breeding behaviors is is little wonder that so many hobbyists become entirely captivated and immersed in this amazing field

check out these excellent resources for breeding success!
Keeping and Breeding Bristlenose

Breeding Discus