Livebearers

Among the hardiest and most versatile of tropical fish livebearers are a popular choice for first time aquarists. Mostly peaceful and sociable, they fit in well in community tanks. They're always active and will provide you with plenty to watch.

The term 'livebearer' refers to any fish which incubates its eggs inside its body. Some do this simply by containing the eggs within a cavity, whilst others provide nutrients to the eggs from their own blood via an organ analogous to the mammalian placenta. When they are born, the fry tend to be larger and better developed than those hatched from eggs laid outside the body. This gives them a better chance of survival, especially in a crowded community tank.

Most livebearers are omnivorous, but it's especially important to make sure they get enough vegetable matter in their diets. Commercial preparations made with spirulina algae are good, as are blanched bits of spinach leaf. Livebearers can adapt to a variety of conditions but tend to do best in slightly alkaline water.

Types of Livebearers

There are quite a number of livebearer species available, but the most popular choices for the aquarium fall into the following groups:

• Guppies -The most popular of all aquarium fish, these tiny fish are highly sociable and beautiful to look at, with each individual having different colours, the males especially vivid. They can be happy in both freshwater and marine tanks.

• Mollies -Including the popular black molly and exotic sailfin molly, these fish can grow fairly big and are highly active. They are very hardy and some species are comfortable in marine aquariums.

• Platies -Fast, active and highly sociable, these charming little fish do best on a diet which contains plenty of live food.

• Swordtails -These brightly coloured, energetic fish like to jump, so make sure your tank has a secure hood. They prefer slightly salty water. They should not be kept with goldfish.

You may sometimes see seahorses and pipefish described as livebearers, though they are not true members of this group, as in their case it's the male who incubates the eggs after they've been deposited in a special pouch in his body.

Breeding Livebearers

Most livebearers do not require much encouragement to breed. The males are easily distinguished from the females because their anal fins are partially fused together into a point. Males can be aggressively possessive of their mates, so you should make sure you have at least three females to every one male in your aquarium. Swordtails sometimes change sex from female to male, though this is more likely if there are no males already present.

Most livebearers breed every four to six weeks; you'll know they're ready when you see the female's belly swell up. They eat their own young, so you might want to consider separating the fry when they appear, or at least providing an environment with plenty of hiding places - lots of plants and pieces of bogwood are a good idea. Feed the parents and other aquarium inhabitants well to discourage predation. Avoid using power filters which may suck in and kill the fry.

Many species of livebearer fry are capable of eating powdered flake food from the start, but they will do best in an aquarium where there are plenty of small protozoans available. If separated, they will thrive on liquid fry food.

Livebearers are so easy to keep and so much fun to watch that they're highly recommended for beginners. They also provide a great opportunity to become familiar with breeding fish. They enjoy living in large shoals, and there are so many colours and varieties available that it's easy to fill a tank with them. They may be a practical choice for the first fish you keep, but you're likely to find that you continue to enjoy them for a long time.