Greater Siren (Siren lacertina) $25 each, plus shipping, are available most of the year. These freshwater aquatic salamanders have external gills, small front limbs, absent hind limbs, and can live 20 years or more and grow to about three feet+ in length. Sirens also gulp air at the surface to aid in breathing, and can tolerate relatively low oxygen levels and higher temperatures. Sirens are both predators and scavengers, foraging along the bottom via touch and smell. These traits make them an ideal aquarium species because they are easy to keep. These interesting animals are also good as display animals and for the science classroom and are one of the easiest and least expensive species to keep.