A visit to your local pet store will make it obvious that in the aquarium hobby, some fish are more popular than others. One such group is the genus Xiphophorus, which contains the platies and swordtails. These fish are perennially popular with aspiring freshwater aquarists, which is easy to understand, given that they are inexpensive, hardy and easy to breed.
When shopping for healthy swordtails and platies, look for signs of stress or disease. Healthy individuals are active, robust and have a good appetite. Some shop owners won’t add food to the aquarium for you to observe that the fish are feeding (because they’re on a specific feeding schedule that they don’t want to deviate from), but in these cases you can observe if the fish are actively searching for food or possibly grazing on any available algae.
Want to read the full story? Pick up the July 2009 issue of Aquarium Fish International, or subscribe to get 12 months of articles just like this.