Swordtails are perennial favorites in the aquarium. They are colorful active swimmers that are fun to watch. Both hardy and undemanding, swordtails have a distinctive ray that extends out from the caudal fin of the male. This elongated tail gives it its unique appearance and a healthy male specimen can be eye-catching in a well-planted tank. A native of Southern Mexico and Guatemala, the swordtail (Xiphophorus helleria) belongs to the family Poeciliidae, and is related to the molly, platy and guppy. It grows to a length of 4 inches (without the sword) and is a colorful and peaceful addition to a community aquarium.
Prepare the aquarium by providing slightly hard, alkaline water between 70 degrees F to 79 degrees F. Swordtails are active, so a filtered, 10-gallon aquarium is the smallest size you should consider. A 25- to 30-gallon community tank would be ideal.
Provide lots of floating plants and vegetation. Swordtails like algae and can often be seen scraping algae from the sides of the aquarium. To insure a good supply of vegetation, make sure the tank receives a few hours of indirect light each day.
Supplement their vegetation by floating a washed, raw spinach or lettuce leaf in the aquarium occasionally. Remember to remove it after a few hours in the tank.
Select fish that are active and have erect, well-shaped fins. Fish that are sluggish or pale may be ill or have trouble adapting to a change of environment. The best candidates will be curious and lively.
Observe fish carefully for the first 72 hours after introducing them to the aquarium. They should be actively exploring their new environment within the first few hours, not hiding.
Allow fish to become acclimated before feeding them. When feeding new fish in the aquarium, less is more.
Feed swordtails dry flaked food, supplementing it with live food occasionally. Brine shrimp and mosquito larvae are welcome additions to their diet.