How Fish Spawn
Live Bearers - Fry are born, not hatched.
These fish give birth to fully developed free swimming fry.
The gestation period is usually around a month. Most fry will need to be protected from their parents, as they will attempt to eat their own fry. There is absolutely no parental care involved. Live Bearer fry will accept ground up flake food as well as baby brine shrimp and micro worms at birth. This group includes Mollies, Guppies, Swordtails and Platies among others.
Egglayers - Fry are hatched from eggs.
Egg Scatterers - Lay their eggs indiscriminately around the tank, they give no care as to where the eggs may fall except to hunt them down to eat them. Fry usually hatch within 24 hours, but don't become free swimming for another 2 - 3 days. Fry will need the tiniest of live foods to get off to a good start, if not available you can use "egg layer" tube fry food. This group includes Danios, Barbs, and some Tetras.
Egg Hangers - These fish lay their slightly adhesive eggs attached to plant leaves, roots, bog wood, and/or other similar items found in the water, including the sides of the tank in an aquarium. This group includes Goldfish, Plant Spawning Killifish, some Tetras and Rasboras, Pencil Fish, most Corydoras catfish, White Clouds and Rainbow Fish.
Bubblenesters - This group of fish lay their eggs in a previously built (by the male) bubble nest. The male will usually look after the fry until they become free swimming. This group consists mainly of Bettas and Gouramis and other Anabantoids.
Cave Spawners - This group consists mainly of Cichlids. The spawning act is usually performed inside a selected cave, the eggs are deposited on the sides or roof of the cave. The female will usually take charge of the eggs and fry, defending them well after they become free swimming and will cease only after the fry are removed or she has another brood. Members of this group are Kribensis, Apistogrammas, some Gobies and some Catfish.
Rock/Leaf Spawners - Similar to the cave spawners except that the action is centered around a rock, leaf or piece of slate. This group includes some Gobies, Angelfish, Discus, Oscars, Firemouths and most other large cichlids.
Mouthbrooders - Eggs are laid in a place like a cave or rock but (depending on the species) the male or the female will take the fertilized eggs in their mouth for incubating. The fry are well looked after by the parents as with the cave spawners and rock spawners. A small group which includes a few Cichlids such as the Egyptian Mouthbrooder, and a few Anabantoids.
Soil Spawners - Almost exclusively a Killifish spawning method. Eggs are buried in the substrate and left to sit through the dry season when the ponds dry up. The eggs remain viable until the rainy season returns and the fry hatch out.