Tag Archives: breeding needs of tropical fish

Live bearing fish in a home aquarium

In several other posts we have looked at fish breeding. We learned about fish that scatter their eggs and fish that hide or anchor their eggs. Fish that harbor their young within their bodies are called livebearers. This group of fish sometimes harbors the eggs in the mouth of the parent and sometimes in the abdomen.

There are about 4 species and a couple of sub-species commonly that are used in a fish tank aquarium. Included in this group are Mouth-breeding Betta, Moffat’s, Gunther’s Cichlid, and Black-chinned Mouthbreeders. In this method of spawning, the female drops her eggs and they are fertilized by the male. Then the eggs are picked back up and kept by one of the parent fish in the mouth until they hatch. The mouth of the parent is not only an incubation chamber, but after the young hatch, a place of safety to dash into in case of danger. Watching the young dash for safety can remind one of people rushing into the New York subway during rush hour.

Many more species of common fish tank fish retain the eggs within their abdomen, and include more than 20 species and several subspecies. Some of the more common to a home aquarium are the Guppy, Molly, Swordtail and Platy. Some of these species will inter-breed in captivity. This knowledge has given amateur and professional breeders a field day in producing many variations in colors and bodies that would not occur in nature.

Animals that retain fertilized eggs within their abdomens are called ovoviviparous. Eggs are produced and then fertilized internally by the male as he swims along beside the female, and the fertilized eggs are carried within the abdomen until they hatch. (This is not the same situation as found in mammals. Mammals not only retain the eggs, but set up a nourishment system from the mother to the young through the placenta. Ovoviviparous species simply retain the eggs and do not provide a maternal nutrition source.). Additionally, in some species the female fish can retain sperm cells for many months and as many as 8 broods have been produced from a single insemination.

As a general rule a well-fed mother will not eat her young. This does not say that other fish in a community tank will not feed on the newborns.

Fries can be produced and survive in a community tank. However, if the expansion of your fish population is your goal, a properly setup breeding tank will give you better results.

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Breeding fish in a home aquarium

The usual fish tank aquarium is set up for the enjoyment of the observer.  An aquarist will often buy a pair of fish, a male and a female. As with other creatures when a male and a female get together the natural impulse is to breed.  A natural question might be, ”Why doesn’t the aquarium soon over flow with fish?”  One of the answers to such a question is related to the breeding needs of tropical fish.

In some cases, fishes in captivity do not acclimate to aquarium conditions.  Even though they may be kept alive and in good health there is “something” missing.  The missing element could be one thing or a combination of things.  It might be that the water pressure is not right for that breed of fish to spawn.  For some fish there is a need for a lot of surface water and even a large fish tank cannot provide enough surface water. Some fish are rendered sterile under normal shipping conditions. Not all the reasons are known and most are speculation.

For the fish that do breed in a fish tank aquarium, the usual community tank does not give enough protection for many of the fry to survive.  This is especially true for the egg scatterers.

Egg scatterers comprise a large portion of the commonly used tropical fish population.  Included in this group are the Tetras, Pencilfish, most of the Barbs, some of the Minnows, Hatchet, and Catfish as well as many others.  The process is just as the name implies.  The female swims and scatters her eggs; the male follows behind her and fertilizes them. An observer sees this behavior as a chase.  Other fish in the tank see this as a feeding.  Even the parent fish will enjoy the roe once the spawning is completed.

A few of the fertilized eggs may make it to the bottom of the tank and find shelter in the aquarium gravel.  The eggs differ in degrees of stickiness to none at all.  The sticky eggs may adhere to an aquarium ornament or plant; some of the eggs may float.  All of the eggs in this group are abandoned by the parent fish making them susceptible to scavengers.  Even the eggs that make it to the safety of aquarium sand or gravel have only a slight chance of maturing into fry. Bottom feeders and scavenger fish will eat most of them.  If an egg should be able to hatch their chances of survival are next to nothing.  The fry are non-swimmers until the yolk sac is absorbed and a lack of an appropriate food source will also inhibit the small fish’s chances of survival.

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