The Aquarian's Net

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The Tourquoise Rainbow is one of the many stunning rainbowfish.

This class of fish includes most of the fish on the planet.  For this type of breeding the most important thing is a watchful eye, as these fish almost without fail will devour any eggs that they see.  Frankly this category should be split up at least 3 ways.  Rainbowfish, Killifish, and then the Tetras & Barbs, however, I’m not the best person to go into depth about the differences between the 3 types, so I’m looping them together here.

Egg scatters generally require softer water and lots of plants.  They typically will lay eggs either on a plant or on the substrate.  For rainbowfish, a “mop” is usually used.  The mop consists of yarn, cotton, not nylon, that is strung together to look like a mop.  It is hung in the tank and will almost certainly be where the fish lay their eggs if there are no bushy plants in the tank.  After the eggs are laid, remove the mop to the hatching tank.  Something that most egg scatterers have in common is that they require very small food when they hatch as the fry are near microscopic.  Again I recommend OSI’s microfood, but a better food would some very small live food, such as smaller strains of freshwater paramecium.  Most people don’t raise those in their homes, so OSI’s food is a good, though inferior substitute.  Breeding of rainbow fish does not require a large tank.  Most rainbowfish can be breed in a tank 20 gallons or smaller, though I suggest keeping the adults in a larger tank.  Males tend to look nearly identical to females in color.  In some species, the males will have a bright yellow crest when they are breeding and/or early in the morning.  In most species, the males have a different shape to their heads.  Whereas the females have a rounded head, the male’s heads are round on the top, but then hit a near 90 degree angle and flatten out as they head down the snout.

Killifish are unbelievably beatiful fish that have to be seen to be believed.

For killifish you can also use a mop, but some fish will lay their eggs in the substrate.  It is usually recommended to have either peat or java moss as a substrate as it will help to hide the eggs from the parents.  The parents should be removed immediately after spawning.  Killifish are quite colorful, that is the males are quite colorful.  The females tend to be rather neutral in coloring.  Usually you don’t want to keep more than 1 male in a tank as they fight voraciously.  Since most killis are annual fish, that is they seldom live longer than a year, they grow quickly and breed freely.  The fry are similar in size to rainbow fry, and I recommend feeding them in the same way.

Tetras & Barbs are the hardest to breed of this group in general.   Whereas Killis and Rainbowfish breed freely if you just put them in a tank together, many tetras and barbs require specific water requirements in order to breed.  In fact if the water pH is off by as much as .2 some tetras will not breed.  In general these fish don’t require too much to breed.  They scatter their eggs on the ground, so many people use marbles or some other porous item on the bottom that allows the eggs to drop so that they can be safe retrieved after the fish have finished breeding.  Fry are again very small and very numerous.  There will be high canabalism and death rates unless you can find an extremely small food, preferably live, to feed them.  The freshwater paramecium is a perfect candidate, but the water it lives in is toxic, so much precaution must be taken.

The first type of fish is generally the fist type of fish that fish-keepers breed.  It is often the doorway into the hobby for people, but it is also under-appreciated.  The guppy in particular offers great opportunities for creating new color strains that are unavailable elsewhere. (for information on doing so, please read Guppy Breeding--For Experts!)

The guppy is one of the best known aquarium fish.

Breeding these fish is not particularly difficult.  Livebearer males posses a gnopodium that makes them easily distinguishable from females.  It resides between the anal fins and is somewhat long and circular.  In many species males are also much more colorful and posses more finage than the female.  This is particularly true with the guppy and some species of swordtail.  In most all livebearer species, the female is much larger than the male.  This is always true when the female is pregnant as it is carrying 20-400 young that will be fully free-swimming and of a well matured size when they are born. 

To actually breed the fish, just put some males and females together.   As these fish are very peaceful, you should have no trouble getting them to breed.  Females will carry the eggs for about 24 days at which time the free-swimming young will be born.   The only difficulty you will have is getting the young out of the tank before they are devoured by the other fish in the tank.   To help in this endeavor, there are many “breeding traps” that are available commercially.

The young are easy to raise and can immediately be feed commercial flake that has been well-crushed.