Axolotl

Quick facts

Adult size

25 cm

Lifespan

can live up to 15 years

Tank zone

bottom

Temperament

peaceful

Difficulty

intermediate

Water parameters

Temperature

14–20°C

pH

6.5 to 8.0

Hardness

7 to 18 dGH

Tank requirements

Minimum volume

75 L

Minimum length

75 cm

Flow

low

Lighting

dim preferred

Substrate

sand

Hiding spots

needed

Open swimming room

needed

Feeding

Diet: carnivore, feeds primarily at the bottom.

Earthworms (nightcrawlers) are the ideal staple food. Frozen bloodworm cubes for juveniles. Sinking carnivore pellets are accepted by some individuals. Hand-feeding with tongs is common; axolotls have poor eyesight and snap at movement.

Nocturnal feeder; drop food after lights out so it can eat without competition.

Compatibility

• Not a fish. A neotenic salamander that retains its larval form (external gills, aquatic lifestyle) for its entire life instead of metamorphosing. Kept in aquariums, sold in fish stores, uses the same filtration. Included here because that's where people look for care information
• Best kept species-only. Will eat any fish small enough to grab. Fish will nibble axolotl gills, causing infection. The combination rarely works long-term
• No gravel. Axolotls swallow substrate while feeding and gravel causes fatal impaction. Fine sand or bare bottom only
• Cold water. Above 22°C causes stress; above 24°C is dangerous; sustained heat above 26°C is often fatal. Cannot be kept in a heated tropical tank. A chiller or cool room is required in warm climates
• Can regenerate limbs, gills, and even parts of their brain and heart. This is why they're one of the most studied animals in developmental biology
• IUCN Critically Endangered in the wild. Native only to Lake Xochimilco and Lake Chalco near Mexico City; Chalco was drained and Xochimilco is heavily polluted. The millions in captivity descend from a small laboratory colony

Habitat

Endemic to Lake Xochimilco in the Valley of Mexico. Critically endangered in the wild, with fewer than 1,000 individuals estimated in their native habitat as of recent surveys. The species is a neotenic salamander, meaning it retains larval features (external gills, aquatic lifestyle) throughout adulthood instead of metamorphosing. The vast majority of pet axolotls descend from a laboratory colony established in the 1860s. Available in several color morphs: wild type (dark olive-brown), leucistic (pink with dark eyes), albino (golden with red eyes), melanoid (solid black), and GFP (fluorescent, a lab variant).

Breeding

Breeds readily in captivity when given a temperature drop. Cooler water (14–16°C) for 2-4 weeks followed by a gradual return to 18–20°C triggers spawning. Males deposit spermatophores on the substrate; females pick them up and lay 200-600 eggs over 24 hours, attaching them individually to plants or surfaces. Eggs hatch in 14-17 days. Cannibalism among juveniles is common; separate by size early. Fry eat live brine shrimp nauplii, then chopped blackworms as they grow.

Common problems

Fungal infections on the gills are the most common health issue, usually caused by poor water quality or elevated temperatures. Axolotls have no scales and absorb toxins through their skin, so water quality must be excellent. They will eat gravel and can die from impaction; use sand or bare bottom, never gravel smaller than the axolotl's head. Floating at the surface is usually a sign of constipation (from overfeeding or swallowed air), not a swim bladder issue.

Bioload

Bioload coefficient: 7.0 (large carnivorous amphibian; produces substantial waste including shed skin mucus).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size