The egg scatterers include many species of tropical aquarium fishes – such as the Danios, Barbs, Rasboras, and Tetras. Even the Goldfish is among the group of fish that scatter their eggs among plants and gravel, both in nature and in an aquarium, while offering no parental care whatsoever! In fact, given the opportunity, most egg scattering fish species will eat the eggs they have just laid and fertilized as soon as the breeding process has finished.
Adhesive and Non-Adhesive Eggs
Most species, like the Barbs and Tetras, lay adhesive eggs that stick to plants as they are laid, but some, like the Zebra Danio, lay non-adhesive eggs that fall to the bottom. The typical spawning movement is a chase of the female by the males, accompanied by spasms of egg-laying and simultaneous sperm ejection and fertilization. Breeding activity may continue for an hour, or in some cases, like with the White Cloud Mountain Minnow, for several days, but a few hours is generally the rule. After spawning is complete, the fish go back to their normal activity, searching for food, including their own eggs. Nearly all egg scatterers will eat their own eggs if given the chance.
The Challenge of Breeding and Rearing of Young
With egg-layers, the challenge is in the breeding itself and then the rearing of the young. Most of the egg scatterers that have been tank and farm-bred for many generations will breed readily in aquarium conditions if the correct water quality and temperature are provided. Water changes often stimulate breeding.
To start breeding, it is important to give the fish the best food possible. Live brine shrimp are ideal, but frozen brine shrimp and freeze-dried foods such as tubifex worms are good too. Give this in addition to a good quality flake food. Set up a breeding aquarium, usually a 10-gallon tank, that is about half full of aged water, and has an air stone with gentle aeration, or a sponge filter in it. Add a small amount of gravel on the bottom, or even pebbles or marbles for egg scatterers, so the eggs will drop out of the reach of the parents. For fish that lay eggs on the plants, place the roots of many plants in the substrate around the periphery of the aquarium, leaving the center open for the fish to swim in. Fine-leaved plants are preferable for attaching the eggs onto. Most of these fish spawn in the morning, so providing low light conditions will also aid spawning.
Use several pairs of mature fish and place them into the breeding aquarium, and usually, within a few days, they will start to spawn. In most egg scattering fish, the only difference observable between males and females is that the females will get a rounded belly when full of eggs and ready to spawn. The males will chase the females around, and fertilize the eggs as she lays them on the plants (for adhesive egg species) or as she scatters them among the rocks on the substrate (non-adhesive eggs). Several hundred eggs may be laid by each female.
The eggs are laid on plants, or on the bottom of the aquarium scattered on the gravel. Once the eggs hatch in the wild, the fry (young fish) have to avoid parental cannibalism, usually by hiding in the plants and among rocks, until they grow large enough to swim freely. In aquariums, it is best to remove the parent fish after they lay the eggs and let the eggs hatch and the fry grow in the breeding aquarium by themselves.
Feeding may be the worst problem for the uninitiated, as the baby fish will need very fine foods to eat. Feeding live infusoria is one of the best foods for baby fish. Live are frozen brine shrimp nauplii are also great first foods. There are also commercial fry foods available at pet stores, and you can feed the fry finely ground flake food as they get bigger.
Improving Methods of Breeding
Many methods for the spawning and raising of different species of egg-layers are available. Fish living in their wild, natural habitat come from different water conditions, weather conditions, available food sources, and other factors than when they are kept in an aquarium. However, unless you are trying to breed fish that have been collected in the wild, basic aquarium water conditions are usually suitable for the breeding of commercially available tropical fish that have been raised on farms.
Perhaps the best general advice is that few species are actually as particular about conditions for successful spawning as most people think, and that cleanliness, healthy fish, and proper feeding are usually more important than fussing about with pH, temperature, light, shade and so forth.
More Good Egg Scatterers To Try Breeding
If you try one or more of these species you will gain a better understanding of nature, and a greater appreciation of our gratifying hobby; fish keeping. Breeding fish will help you enjoy our great hobby more each day!
Arantes, Fábio P et al. Influence of water temperature on induced reproduction by hypophysation, sex steroids concentrations and final oocyte maturation of the “curimatã-pacu” Prochilodus argenteus (Pisces: Prochilodontidae). General and Comparative Endocrinology, vol. 172, no. 3, 2011, pp. 400-408. doi:10.1016/j.ygcen.2011.04.007