An Axolotl (Scientific name: Ambystoma Mexicanum) although commonly called a Mexican Walking Fish, is not actually fish but an amphibian. The axolotl is closely related to the Tiger Salamander. Axolotls do not undergo metamorphosis from their larval stage like other amphibians; instead they retain their gills and remain aquatic. They can grow to over 43cm (17 inches), but average between 20 and 28cm (8-11 inches). Natural wild colours are dark grey, brown or black with albino, pink and white more common among captive bred varieties.
Natural Range and Habitat
Originally only found in Lakes Chalco and Xochimilco in Mexico City they are now listed as critically endangered in the wild by CITES due to habitat loss. Lake Chalco was drained to prevent flooding and Lake Xochimilco survives only as a serious of canals. It is highly likely they are now extinct in the wild. A 4 month survey in 2013 failed to find any specimens in the remnants of Lake Xochimilco. The population had been in decline; a similar survey in 1998 found 6000 per sq. km but only 100 per sq. km in 2008.
Axolotls are easily kept in an aquarium environment. They never leave the water so a land feature is unnecessary. A sandy base is preferred over gravel, to prevent death from choking as the axolotl will attempt to swallow anything smaller than its head. Recommended aquarium size would be at least 60 x 30 x 37cm (24 x 12 x 15 inches) with a water depth of 15cm (6 inches) minimum. Water temperature in the wild would vary between 6 degrees C (43F) in winter and 20 degrees C (68F) in summer. Higher than 25 degrees C (77F) for more than a few days and axolotls suffer from stress. Stress may result in illness and death due to fungal or bacterial infections. Water circulation is important, but fast flow is not recommended so a spreader should be used. They do like to hide sometimes, so some traditional aquarium furniture can be ideal.
Axolotls are carnivorous; eating worms, molluscs, insects and small fish in the wild. They feed by sucking food in like a vacuum cleaner (reason why gravel should be avoided as a floor substrate). In an aquarium environment they will eat earthworms, bloodworms, shrimp, pieces of fish, strips of beef, insects and tadpoles. The sinking food sold for trout and salmon is ideal. Do not overfeed or leave uneaten food in the water. What they can eat in 15 minutes every 2 to 3 days is usual.
There is a thriving population of axolotls in captivity due to their benefits for scientific research. Axolotls have a unique healing and regenerative capability, namely being able to regrow lost limbs. Males are usually ready for breeding when they reach approximately 20cm (8 inches) in length at around six months of age. Females, ideally should be around 18 months old though before breeding. Average litter size of eggs is around 500 with a range of 100 to 1000. The female will require plants in the aquarium (plastic won’t rot) to fix the eggs to. The eggs hatch after only 11 to 14 days. December and January seem to be the most successful months for breeding.