Courtship and Breeding in Freshwater Fish
Dr. Amy Wolff
It's a common occurrence. You've started with a simple tank, mastered the nitrogen cycle, basic water chemistry and have tried a number of different fish and found a few species that have become your favorites. You begin to think about the challenge of a breeding tank or providing the right conditions in your community tank to encourage reproduction. Your fish may have blessed you with babies without any effort on your part, but here are a few tips on what to expect and how to provide the right conditions for breeding popular varieties of freshwater fish. The species discussed here are considered to be the easiest and most successful fish to breed for the average hobbyist.
Before you begin, you must decide whether or not you want to encourage breeding in a community tank or a breeding tank. A breeding tank is an environment set up for the sole purpose of producing and raising the fry. Breeding tanks lack the decorative accessories of a community tank or show aquarium. Filtration, aeration, proper nutrition and water quality are the only priorities. Breeding in community tanks is more challenging. Some varieties will crossbreed within a species so keeping offspring true to type may be difficult. Also, parents guarding eggs or fry may become very aggressive towards other members of the community. You may need a breeding box or other small tank to place the young. They can become fish food to many of the tank inhabitants!
Guppies, Swordtails, Platys and Mollies
These popular fish belong to a group known as the "live-bearing tooth carps. Their babies are born alive and have the advantage of being immediately free-swimming and able to hide from predators. These fish breed easily without too many inducements. Males in these species are easy to distinguish from females in that they are larger, have more prominent fins and colors, and have a specialized pelvic fin called a gonopodium, which is used to impregnate the female. A single male can chase and exhaust a single female, so these fish usually do better in a harem situation. Females can have several separate pregnancies from a single breeding, often to the surprise of the hobbyist who has kept a female without the presence of a male! The gestation period (time of the pregnancy) varies, but averages from 4-6 weeks, slightly more for mollies. The number of fry produced varies greatly, from 10-100 babies, which are mature in about 6 months. A pregnant female is easy to spot by her swollen belly and dark spot (i.e. gravid spot) of developing embryos located at the base of the tail. As delivery time approaches, the female should be placed in a breeding box to protect the fry. If breeding occurs in a community tank, dense plantings should be available so the babies have cover.
There are literally hundreds of African cichlid species. The reproductive habits of these fish can vary, so if you are interested in a particular species, it's best to get specific information. The types most often bred are called mouth brooders because of the parent's habit of protecting eggs and young in their mouths. These fish lay eggs and both parents participate in protecting the fry. It is not always easy to tell males from females. Usually, a group of small fish is purchased while they are young and begin to reproduce between 8 and 12 months of age. A female may lay eggs at several sites in the tank or may hold them in her mouth. Once the eggs are fertilized, these normally aggressive fish will become extremely territorial and other tank mates are at risk. The eggs incubate for about three weeks. Once they hatch, the females may abandon them or guard them fiercely, depending on the species. In a community tank, cichlids should be given a tank with caves and lots of rocky outcroppings. They will dig in gravel, especially at breeding time, so your tank can get re-arranged easily.
Beautiful angelfish can put on quite a courtship display. Breeding pairs establish a territory and defend it. They may push and shove each other and even engage in "lip-locking. The usual plan is to buy a number of larger fish and place them together in a tank and watch for pair formation. Once you know who is dating whom, you can place breeding pairs in a separate tank. Multiple breeding pairs in a community tank can cause disputes and injuries. The female will want a surface on which to lay her eggs. Slanted rock, slate or sword plants are preferred. The fish will inspect and clean the spawning surface. Once it meets her approval, the female will begin to lay rows of eggs. The male follows after her and fertilizes them. Both parents fan the eggs to improve water circulation, keeping them clean and free of waste and fungus. The eggs hatch in about 3 days. The fry retain their yolk sac for 2-3 days so they will sink to the bottom of the tank until it is absorbed. During this time, the parents may eat them so watch carefully; they may need to be removed. Once the yolk sac is absorbed, begin feeding the new fry with brine shrimp or other fry food.
Siamese Fighting Fish (Bettas)
Bettas belong to a group of fish known as labyrinthine fish. Males and females are easily distinguished; males have striking colors and beautiful long fins compared to the drab females. They are usually separated until breeding time. The male will display for the female and constructs a bubble nest, an intricate floating nest of air bubbles held together by mouth secretions, which the male constantly repairs. Breeding is difficult and exhausting for the female. The male wraps his body around the female and squeezes her until the eggs are delivered. This may occur several times. The male collects the eggs and places them in the nest, which he guards. The eggs hatch in 2 days and the male guards the babies for another week or so.
These Australian natives are peaceful and breed easily in a community tank. The males are larger and more intensely colored than the females. Eggs are laid on plants in the tank suspended by small threads. They will hatch in 12-20 days depending on water and temperature conditions. True to their peaceful nature, the rainbows do not consume their eggs or fry, but other fish in the community might! It is best to feed the fish in a community tank well when there are babies present to keep them from taking a snack.
Barbs are egg layers and there are a lot of species. They like a heavily planted tank and some species prefer dim lighting to induce spawning. The female may lay as many as 300 eggs and they hatch in 24-36 hours. Parents may make a meal of the fry so it's best to remove the adult fish. Dense foliage provides good cover for the babies.