Even when placed in an aquarium, they spend the bulk of their time lying nearly motionless at the bottom. They are extraordinarily resourceful when it comes to gas exchange. If you watch an axolotl for several minutes you will see it flick its gills periodically. Moving the fronds back and forth quickly stirs up the surrounding water and disperses any carbon dioxide that may have accumulated about the gills and mixes in fresh, oxygenated water. Although we successfully use plastic containers, they must be kept very clean.
Plastic tends to support the growth of a bacterial scum along the bottom and sides of the container.
We have found that if this scum is not cleaned off periodically, the axolotls will develop sores on their toes and feet that will not heal. Instead the skin retreats up the leg and the toes eventually die and are sloughed off. If this happens put the axolotl temporarily into a glass bowl. The axolotl will heal nicely, and the toes will probably regenerate. When they first hatch, fifty or more larvae may occupy the same bowl, but as they grow, reduce the number per bowl progressively.