Livebearer Fish

Livebearers make an excellent introduction to the fishkeepinghobby. They are hardy, active, easy to maintain and easy toinduce into breeding in the aquarium. So what is a livehearer?iWell, all the fish discussed so far are egglayers, i.e. fish that layeggs and then fertilize them outside the female's body. In livebearers, theeggs are retained within the female's body after fertilization and theembryos develop for about one month before being released. When thefry are released, they are usually exact miniature replicas of the female.In some species this process can be repeated every two months.

All male livebearers have a gonopodium, a modified anal fin used bythe male to spray his sperm at the female's vent to fertilize the eggs.After four or five weeks, the female will he ready to release her young.She develops a 'gravid spot', a dark, swollen area on the lower part ofthe abdomen, just in front of the anal fin. She will try to release theyoung in a quiet spot near a clump of plants and, although they hide inthe vegetation, other fish - even their parents - regard them as food. Youcan protect the fry by using a breeding trap.

A pair of greenvariegated delta tail guppies(Poecilia reticulata). Thelower fish is a male with asplendid tail, but even thefemale fish - normally drabcompaifd to the male - hasbenefited from the breedingprogramme and sports astriking tail. The name'guppy' comes from thenaturalist Robert Guppy,who first collected the fishesin Trinidad in the 1860s.

A marbled form of the blackmolly (Poecilia sp.) that grows toabout 7.Scm(3in) excluding the tail.Mollies eat most flake foods and alsorelish live or freeze-dried Daphnia,hloodworm and brineshrimp. Offerthem some vegetable matter, such asgarden peas with the skins removed.Black mollies prefer a temperature of 26°C(79°F) - higher than normal forcommunity tropicals. Like their closerelative the guppy, these fish are easyto breed but can be a little nervous.They are best bred in a tank of theirown, where they produce broods of10-40 fry. There is an aquarium-bredstrain of the black molly with aforked tail, known as the lyretail.

Mollies

In the wild, mollies are usually found in quite hard water areas andriver estuaries, so it is a good idea to add a desertspoonful of sea salt toevery 23 litres (5 gallons) of tank water. Black mollies also like someplants in the tank to give them cover and to nibble at. If you do add saltto the tank, make sure that other fish and any plants can withstand thebrackish conditions, or use plastic plants.

The black molly (Poecilia sp.) is something of an unknown quantityin that it is a hybrid and nobody seems to know from which two speciesit was bred. This fish breeds true to coloration and produces viableyoung, which should not be the case with a hybrid. There are alsomarbled, albino and green forms.

Platies

The platy is another common livebearer from Mexico and other partsof Central America. Male fishes grow to a maximum length ofScm(2in), whereas females are often a little larger. These quite plumpfish have slightly upturned little mouths for feeding from the surface.The dorsal fin and tail are very rounded. Tank-bred fishes often hearlittle resemblance in colour to their wild counterparts. In the absence ofmembers of the opposite sex of their own type, platies and swordtailswill crossbreed. Try to prevent this if at all possible.

Swordtails

The swordtail is very much like the platy, but in males the bottom rayof the caudal fin extends to a very long point, like the blade of a sword.As in the platies, there are many colour variants of this species, somewith extra long dorsal fins and anal fins, too. When buying a maleswordtail, check that its anal fin has not developed in this way, as it willhave trouble spawning with females. Swordtails prefer slightly alkaline,medium-hard water at 25°C(77°F)