Swordtail

Because they are larger and more active than platies, a group needs a minimum of about 80 litres, and a longer tank is better for these powerful swimmers. Plant the edges and leave open central swimming space, and above all fit a tight fitting lid, since swordtails are notorious jumpers that will leap from an open tank. Keep the water filtered and heated.

Swordtails are omnivores, so feed a good quality flake or pellet as the staple, with added vegetable matter or algae and occasional frozen brine shrimp or daphnia. Offer small amounts once or twice a day that they finish quickly, and avoid overfeeding, which quickly pollutes the water in a busy, active tank.

Keep the water at 22 to 26 degrees Celsius, pH 7.0 to 8.4, and moderately hard to hard, as they share the livebearer preference for harder, alkaline, mineral rich water. The tank must be cycled with ammonia at 0 and nitrite at 0 and nitrate low. Dechlorinate tap water and change about 25 percent weekly with matched temperature water.

Keep more females than males, about two to three females per male, because males are territorial and will chase and harass rivals and females alike. It is often best to keep a single male with several females, or a group with plenty of space and cover to break up aggression. They are otherwise peaceful with other calm community fish and produce regular batches of live fry.

Open swimming lanes are important for these active fish, combined with planted areas and gentle current to swim against. Plants and floating cover give fry a refuge and let subordinate fish escape a dominant male, keeping the group calm and confident.