🐾 Land🐟 AquaticCare difficulty: AdvancedLegal complexity: High — restricted in many states
Greater siren
Siren lacertina · also called Mud eel, Mud iguana, Ditch eel
A massive, eel-like aquatic salamander that keeps feathery external gills for life and has only a single pair of tiny front legs. It is hardy and long-lived but huge, secretive, and powerful, making it a specialist aquarium animal rather than a handling pet. US trade is restricted because the genus is federally listed as injurious wildlife.
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Quick facts
| Size | Very large: commonly 20 to 30 in (50 to 75 cm) and reaching up to about 38 in (97 cm), eel-like with external gills and only tiny front limbs |
| Lifespan | 15–25 years |
| Social needs | solo |
| Native region | Southeastern United States (coastal plain swamps, lakes, and slow waters from Maryland to Florida and Alabama) |
| Origin | New World |
| Climate | ⛅ Subtropical |
| Water type | 💧 Freshwater |
| Family | Sirenidae |
| Genus | Siren |
Part of the Aquatic amphibians
Fully or largely aquatic amphibians kept in cycled, well-filtered freshwater aquariums. They surface to breathe, prefer gentle current and hiding spots, and are not handling animals.
Habitat & space requirements
From the minimum an animal needs to be kept humanely, up to the ideal setup. Bigger is almost always better — minimums are floors, not targets.
Life & growth stages
How this animal changes through its life — each stage often has its own care, diet and space needs.
Habitat & enclosure
House one animal alone in a large aquatic tank with a tight, weighted lid: a 55 to 75 gallon (210 to 280 L) or larger setup with generous floor area and shallow-to-moderate water depth. Provide heavy cover such as PVC tubes, caves, driftwood, and dense plants, since sirens are secretive and hide most of the day. They are perennibranchs that breathe through external gills (supplemented by lungs and skin), so keep water clean, well-oxygenated, and well-filtered. Maintain warm-temperate water around 68 to 78 F (20 to 26 C). No UVB is required.
Substrate
Use a bare bottom for easy maintenance or soft fine sand if a natural look is desired (they like to burrow), avoiding gravel that could be ingested. Prioritize dense cover with PVC pipes, caves, driftwood, and robust plants so the animal stays hidden and calm, which reduces stress.
Equipment & setup
Run a strong, well-baffled filter sized above the tank volume for excellent biological filtration and good oxygenation, and add an air stone to keep the water well aerated for their external gills. A guarded heater holds warm-temperate temperatures. As with other large aquatic salamanders, an absolutely secure, weighted lid is essential to prevent escape. Dim lighting suits their nocturnal habits.
Diet
Omnivorous-leaning carnivore that forages by smell along the bottom. Feed earthworms/nightcrawlers (a staple), bloodworms, blackworms, crustaceans, snails, chopped fish, shrimp, and sinking carnivore pellets; they will also nibble some plant and algal matter. Offer food in the evening every 2 to 4 days, target-feeding near hides. Avoid overfeeding, as they put on weight readily, and remove uneaten food to protect water quality.
Behavior & temperament
Nocturnal, shy, and secretive, spending the day buried in cover or substrate and foraging at night. Generally not aggressive toward people but will struggle strongly if grabbed and can deliver a surprisingly hard nip with its beak-like jaws; it can also produce yelping or clicking sounds when distressed. This is not a handling animal: move it only when necessary with a net or container, never bare hands, and keep fingers clear at feeding time. Keep strictly solo, as sirens can be aggressive toward tankmates and conspecifics. During droughts in the wild they estivate in mud cocoons.
Health
Hardy when water quality is maintained, but sensitive to ammonia, nitrite, and chlorine; poor conditions cause gill deterioration, bacterial and fungal skin infections, and red-leg. Healthy external gills should be full and feathery, so degraded or stubby gills signal poor oxygenation or water quality. Avoid copper-based medications. Obesity from overfeeding is common. Provide stable, well-filtered, oxygenated water and ample cover, and quarantine wild-caught animals, which may carry parasites.
Tips, DIY & hacks
Check legality before acquiring: the genus Siren has been listed as injurious wildlife under the Lacey Act since 2016 to slow the spread of the Bsal fungus, so importation and interstate transport are prohibited (keeping an animal you already own is generally still legal). Treat this as a long-term specialist commitment given the size and lifespan. Keep the water highly oxygenated to maintain healthy external gills, the best visual indicator of their wellbeing. Always use a net or container to move the animal and tongs to feed, never bare hands. Provide abundant hiding cover from the start to keep the siren calm and feeding, and keep one per tank.
Sources
- AmphibiaWeb: Siren lacertina (database)
- Amphibian Species of the World: Siren lacertina (reference)
- USFWS: Injurious Wildlife Listings (salamanders, Bsal) (government)
- Wikipedia: Greater siren (wiki)