Axolotls

The aquarium

• Provide
  • a glass tank (not a round, Perspex bowl) as an aquarium with a water-filtering system to keep the water clean
  • gravel with rocks for the axolotls to stand on
  • plants to provide them with hiding places
  • a cover to protect them from predators and to prevent them escaping.
• Keep aquarium conditions clean and at a relatively constant temperature.
• Axolotls are mainly nocturnal, and they are more active in dim light. They have no eyelids to protect their eyes from harsh lights, so it is important to position the tank out of direct sunlight and to provide them with some shelter, usually in the form of plants.
• Anchor all plants well. Plastic plants are best because they will withstand rough treatment from the axolotls. Plastic is also easy to clean.

Setting up the aquarium

• The minimum size for two axolotls is 60 centimetres × 40 centimetres × 40 centimetres high. If they are overcrowded, axolotls will become less active and may even eat each other.
• Prepare the tank by washing it out with salt and water and rinsing it thoroughly.
• Place the empty tank on a flat, solid surface out of direct sunlight. As 1 litre of water weighs 1 kilogram, when the tank is filled with water and gravel, it may be very heavy. Consider what may happen in the event of an earthquake.
• Before using it, rinse the gravel under a stream of water until the water runs clear.
• Follow the instructions to install the filter.
• Fill the tank to a depth of 25–30 centimetres and secure the plants. Turn on the pump and check that all systems are working.
• Leave the water to stand for one day. This allows the chlorine to evaporate. Alternatively, there are chemical products available to achieve this more quickly.
• Axolotls are poikilothermic, that is, their body temperature is determined by the temperature of the environment. Ensure that they maintain a temperature range of 10–25 degrees Celsius (°C). The optimum temperature is 14–18°C.

Filtration

• Filtration maintains good water quality by removing waste.

• There are several types of filtration systems, including:
  • under-gravel filters, which draw water and waste down through the gravel but leave large solid wastes behind
  • reverse-flow external filtration systems, which take water from over the gravel, pass it through an external filter, and then return it to the tank.
• The filter medium needs to be cleaned and/or replaced regularly. With either system, vacuum the bottom of the tank to remove large particles of debris.

Maintaining the aquarium

• Remove faecal material each day, usually with a tank vacuum cleaner.
• How often the water needs changing will depend on the number of axolotls and the type of filtration system used. As a rule, remove and replace one-third of the water each week, remembering to let the replacement water stand in a bucket for twenty-four hours to dissipate the chlorine before adding it to the tank.
• With under-gravel filters, rake the gravel through and remove debris before changing the water.
• With an external filtration system, the filter will need cleaning out and the filter medium may need replacing, usually every two to four weeks.
• Plastic plants will develop an algal growth. Most plastic plants can be washed in warm water and left to soak in a weak bleach solution (10–20 millilitres of bleach per litre of water) for ten to fifteen minutes. Rinse them thoroughly before returning them to the tank.
• Depending on the method of water filtration, thoroughly clean the tank at least every three months.

• feed 2–3 times a week
• use blunt forceps
• strips of beef
• multivitamin supplement.

Aquarium diagram explanation

A rectangular tank measuring 60cm x 40 cm x 40 cm high, sufficient for two axolotls.

It contains a thermometer to maintain temperature at 10–25°C, rocks, well-anchored plastic plants, washed gravel and an efficient filter pump which must be changed or replaced regularly.

It is to be placed out of direct sunlight, vacuumed daily to remove food debris and excrement and cleaned thoroughly every three months.

When refilling tank after cleaning, chlorine must have time to evaporate.

Axolotls should be fed 2–3 times weekly with strips of beef using blunt forceps – a multivitamin supplement is also advised.

^{Axolotis aquarium: main features}

Feeding

• Axolotls can be trained to take a variety of foods, such as worms, insects, freshwater shrimps, and tadpoles, or more convenient foods, such as raw beef meat (trimmed of all fat), liver, beef or lamb heart, and cat food. Mince is not suitable food because it contains preservatives. A popular method of feeding is to cut beef schnitzels into strips 0.5 centimetres × 3 centimetres, wrap them in meal-sized portions, and then freeze them until they are needed. However, if the axolotls mainly eat raw beef, give them a multivitamin supplement.
• The amount to feed varies with the axolotl's size, its stage of maturity, and the water temperature. Axolotls need feeding only two or three times a week because they take two to three days, on average, to digest their food. Digestion will be faster at higher temperatures and slower in cold weather. If the temperature falls below 10°C, they will regurgitate their food.
• It is less messy to feed axolotls by hand, holding the food in blunt/round-nosed forceps in front of the animal. Watch carefully because sometimes axolotls eat little during the day. If that is the case, it may be wise to feed them at night, when they become more active, in order to prevent them from eating each other!

Handling

• Handle axolotls only when it is necessary, such as when cleaning the tank. They can be trapped with a shallow net and then gently grasped with one hand around their neck and shoulders and the other around their abdomen and hind legs. Do not squeeze them because they are easily damaged. When handling them, take care as they often thrash their tails around, which could damage them.
• Handle the animals only with clean, wet hands that have no trace of soap or detergent on them. Take any rings off before handling them and always wash your hands afterwards.

Health

• Learn what is normal behaviour for axolotls and check them daily. Remember that because axolotls breathe through their skin, it must not dry out.
• Incorrect environmental conditions and inadequate nutrition can make axolotls sick. To avoid this, feed them a variety of foods and maintain good-quality water.
• Axolotls can also be affected by viruses and bacteria. At any sign of illness, or if you have questions, consult a veterinarian.
• Beware of ammonia build-up, which is toxic. Ammonia is the main metabolic waste product of axolotls, and it also comes from decomposing food and other organic material. Increased levels of ammonia can also be caused by overcrowding, overfeeding, high water pH, warm water, and new tanks that haven't had time to develop good populations of nitrifying bacteria. Having a good water flow, changing water regularly, and removing uneaten food and faecal material can control ammonia levels.

• Axolotls inhabit an area to the south east of Mexico City. In ancient times, they were eaten by the Aztecs.
• Axolotls (Ambystoma mexicanum) are gilled amphibians. They are unmetamorphosed larvae of the Mexican salamander.
• Axolotls have a cartilaginous skeleton that, even in larger, older axolotls, doesn't become completely calcified. Their muscles are similar to those of fish. They have fine teeth on their upper and lower jaws that they use to grab their food and puncture it. It is thought that this helps their digestive enzymes to penetrate the food.
• Axolotls respire (breath oxygen) through their cartilaginous gills, like fish, as well as cutaneously, that is, by diffusing oxygen that has dissolved in the water through their skin. Larger, older axolotls supplement their oxygen supply by filling their rudimentary lungs at the surface of the water.
• Axolotls excrete only half of their nitrogenous wastes as weak urine. The rest is excreted through their gills.
• Axolotls have no eyelids.

Reproduction and development

• Axolotls are unusual because they are capable of reproduction in their larval state, a phenomenon called neotony. This is usually at twelve months of age.
• Sexing axolotls may be difficult unless there is one of each gender to compare. In the male, the cloaca (the external opening of the intestine) is larger and more swollen around the margins. The male's head is also narrower, and its tail is longer than the female's.
• Their natural breeding season is spring. The length of the day and the temperature of the water are thought to influence the start of breeding.
• Fertilisation is internal.
• They may release 300–1100 eggs per spawning. The eggs are gelatinous and stick to surfaces in the tank. They need good oxygen levels to develop, and their rate of development depends on the temperature.
• Axolotls leave the egg with small feathery gills, a tail, and two outgrowths from the sides of their heads that allow them to attach to a substrate. As they grow, their gills increase in size and they develop legs.
• Small axolotls, especially those less than 10 centimetres in size, often eat each other, but survivors may live for ten to twelve years.