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Axolotl

Ambystoma mexicanum
SynonymsGyrinus mexicanus
DistributionMexico
Sexual DimorphismMature females are larger and fuller bodied. Males have a more pronounced cloaca.
Maximum SizeUp to 30cm (11.8") but usually slightly smaller.
TemperatureSubtropical: 16-22 deg C (61-72 deg F)
Water ParameterspH: 6.8-7.8, dH: up to 20 degrees.
CompatibilitySpecies-only aquaria.
LightingDim, but can be brighter if diffused by floating plants.

Care

The Axolotl is a neotenic salamander that originates from Lake Xochimilco and Lake Chalco in the Valley of Mexico, a highland plateau in central Mexico. Unfortunately, Lake Chalco is no more, as it was artificially drained to avoid periodic flooding and to provide for land expansion. Lake Xochimilco still exists, but only as a shell of its former self, present mainly as a network of canals, many heavily polluted. As a result, this species is critically endangered in the wild; however, it is captive bred in large numbers at numerous aquaculture facilities and specimens for sale in the shops are all bred and raised in captivity. Although known informally as the "walking fish", the Axolotl is not a fish, but an amphibian. It is unusual in that it reaches adulthood without going through metamorphosis. Unlike most other amphibians, it does not develop further and then take to the land - instead it remains aquatic and gilled. Axolotls do have some specialist care requirements when it comes to keeping them in the home aquarium. Firstly, substrate choice is very important - they must not be kept on sharp gravel. This is because they are primarily bottom dwellers and could easily damage the skin on sharp surfaces, and also there is the very real danger of them ingesting pieces of gravel when lunging for food (this can be fatal). Sand is much softer against their skin and does not pose any problems when they feed. Filtration should be efficient, but water movement very gentle. Internal sponge filters are ideal for the Axolotl tank as they provide filtration and aeration without being too vigorous. If an external canister is used, it would be prudent to place a coarse sponge or filter bag/mesh over the intake pipe cage to prevent the Axolotls from being drawn against it and subsequently trapped by the flow. If there is too much water movement in the aquarium, the Axolotl's gills will curl forward, so be sure to adjust your flow if this occurs. As Axolotls are not able to regulate their body temperature internally, they rely on their environment being the appropriate temperature for them to be comfortable, so ensure water temperature is steady and cool. A means of chilling the water may be necessary during particularly hot summers, as a prolonged water temperature above 24 deg C will cause metabolic rate increase and much stress followed by illness and death. Hiding places should be provided amongst smooth rocks, driftwood, PVC pipes, and hardy aquatic plants. Axolotls are largely nocturnal, so prefer dim illumination. Brighter lighting can be utilised, however, if plenty of diffusion is provided by aquatic plants (both rooted and floating) and shady hiding spots. A blue moon light set to come on just before the main lights switch off will allow you to view their goings on into the late evening for a few hours. Regular partial water changes are essential as Axolotls require excellent water quality at all times and will not tolerate a build up of nitrate. With regards to compatibility, Axolotls will prey on anything they can fit in their mouths, including fish that are of similar size to themselves, so they are best maintained in a species-only environment. They can pose a serious risk to each other as well though. Smaller/younger Axolotls are easy targets for larger individuals and these may lose limbs or even be eaten. When keeping a group of Axolotls, be sure to provide adequate space for territories and ensure there are plenty of hiding places (several per Axolotl) and visual barriers amongst the decor. It is important not to overcrowd them and make sure all individuals are of the same size and introduced simultaneously. Axolotls are available in a selection of different colour forms. The standard 'wild type' is an olive grey colour with dark spots and gold speckling. Albino, axanthic, leucistic, and melanistic varieties are also readily available, and a rarer striking black and white piebald variety is highly sought after. As with other salamanders, the Axolotl is capable of regenerating lost limbs over a period of a few months.

Feeding

Carnivorous. Offer a variety of foods including sinking pellets/granules (such as Tetra ReptoMin) and meaty frozen foods such as white mosquito larvae, bloodworm, daphnia, vitamin-enriched brineshrimp, mysis shrimp, chopped krill/prawns.

Breeding

Axolotls breed readily in the home aquarium. They have been triggered into doing so by shortening the photoperiod on the tank, whilst simultaneously increasing the water temperature slightly, then increasing the photoperiod again and bringing the temperature back down via a reasonably sized water change. The adults will predate on the eggs, so you will either need to set up a separate breeding aquarium for this purpose, or have a spare tank ready to move the adults into once the female is spent of eggs. A breeding tank should have some flat pieces of slate on the base for the male to deposit his spermatophores (packets of sperm) onto, and aquatic plants for the female to deposit her eggs. Spawning is initiated by the male, who performs a courtship dance, swimming around, raising his tail and writhing excitedly. The male deposits a number of spermatophores around the tank, and then nudges the female's vent and leads her around the tank, escorting her in the right direction and encouraging her to pick up the spermatophores with her cloaca. Fertilisation takes place internally, and a few hours later, she will lay the fertilised eggs on the aquatic plants. Once the female stops laying, she and her partner should be moved to another aquarium to prevent predation. The eggs should hatch after 2-3 weeks (temperature dependent) and the young, measuring 10-13mm, will require tiny foodstuffs such as baby brineshrimp once they have used up their yolk sacs. Unfortunately cannibalism tends to be rife, and several rearing tanks may be needed so that low numbers (less than 10) can be kept in each tank, separating them into groups by size. Lowering the light level and providing dense planting is also said to help minimise cannibalism.

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