Axolotls (Ambystoma mexicanum)
Axolotls are large, neotenic salamanders from Lake Xochimilico in Mexico. While endangered in the wild, they are very common in captivity and make excellent pets.
Axolotls typically reach an adult size of about 8 or 9 inches in total length, however some individuals may attain lengths of a foot long or more. They prefer temperatures of approximately 65 F but will tolerate slightly warmer for short periods without issue. If temperatures go above 72 F for extended periods, axolotls will become susceptible to various illnesses and infections. In addition to getting temperature correct, the other important thing to consider with axolotls is flow rate. Axolotls are from quiet, still waters and will become stressed if subjected to too much current. A sponge filter with an attached air pump is an ideal way to filter an axolotl tank, but if you wish to increase the filtration level, you can also use a canister filter with the flow dispersed via a spray bar or a hang on the back filter with the flow disrupted by tank decor.
An adult axolotl can live comfortably in a ten gallon aquarium, but larger aquaria are always better and easier to maintain in the long run. Many keepers choose twenty gallon long style tanks because it provides the animals with more floor space, which they will tend to use more than height. Axolotls are fairly gregarious once they are adults so you can keep multiple animals together if desired, but plan about ten gallons worth of water per additional animal. Younger animals have a habit of eating each other's legs if kept together, but fortunately axolotls are amazingly good at regenerating body parts (a big reason why they are often studied in laboratories).
When setting up the aquarium, be aware that axolotls are notorious for ingesting substrate so plan accordingly. Do not use pea-size gravel commonly sold for fish tanks. Large river stones, smooth fine play sand or no substrate at all are all acceptable choices for axolotls. Bare bottom tanks are easiest to clean.
Axolotls do not (with very rare exceptions) undergo metamorphosis like other salamanders, so they do not generally need escape proof lids or screens, but if keeping them without a lid I recommend lowering the water level slightly so there's no chance of your axolotl accidentally leaping out of the water. They do not need any special lighting, but do prefer places to hide if you are going to light the tank. You can keep axolotls with live plants such as java moss, java fern or other cold tolerant plants.
Like many reptiles and amphibians kept in the hobby, axolotls have been selectively bred for various colors and patterns. The most commonly available colors are wild type (gray, brown or black), black melanoid (all black with no shiny irridophores), leucistic (white or pink with black eyes) and albino (white, pink or yellow with red eyes). I will expand on axolotl morphs and genetics in another article. All morphs are basically cared for the same.
Cycling the Aquarium
A quick note about cycling. Cycling a tank refers to the process of establishing the beneficial, nitrogen-fixing bacteria that allow all aquaria to function. There is a lot of information out there about how this works, so I won't go into a ton of detail, but it's important to know that just filling a tank up with water and dumping an axolotl in is not ideal, as it typically takes 3 to 6 weeks to establish beneficial bacteria in an aquarium. If you have access to water or even dirty filter media from an already established aquarium you can use this to "jump start" an aquarium. Be vigilant about newly set up tanks, and watch for ammonia spikes that can harm or kill your animals.
Axolotls are not picky eaters. Adults will eat commercially prepared sinking pellet fish foods, frozen blood worms and live worms of almost any kind. (However, be careful when acquiring wild worms from outside, as they may contain trace amounts of pesticides and other harmful things). Offering a variety of foods ensures good nutrition for your axolotls so mixing it up is recommended. Feed adult axolotls every two to three days and siphon out any uneaten food before it rots. Juvenile animals that are under a year old can be fed daily.
Axolotls are not difficult to breed, and typically start breeding in late fall, however many keepers find they will spawn randomly throughout the year. My animals usually only require a shift in temperature (usually triggered by their weekly water change) to get started. Males will start nosing at the females cloaca and depositing spermatophores around the tank. Shortly after that you will see the female start depositing eggs. I usually use fake plants for this, as they tend to destroy live plants in the process of laying.
Remove the eggs to a nursery tank, as the adults will readily eat them. Keep the eggs at roughly the same temperature and condition you would the adults and in roughly two weeks, the larvae will hatch as half inch long little tadpoles. For a day or two, they won't eat anything, as they're still absorbing yolk. After that, you can start offering live foods.
I raise all my salamander larvae on pond water from outside (as it's free and has tons of nutritious micro-organisms in it) but If you don't have access to pond water, you can use chopped up live black worms, live daphnia moina or live baby brine shrimp. I dislike brine shrimp because, being salt water organisms they all die shortly after being put in the water with the larvae and foul it up very quickly. But many keepers, including a great many laboratories where axolotls are used for experiments use brine shrimp.
Once the larvae begin growing back legs they are generally past the danger zone and will start accepting frozen, non-live foods. It takes most axolotls roughly a year to fully mature into adults.
A Word About Mixing Species
Many people ask if they can mix X species with Y species. My answer is almost always, no. These animals should be kept in a species specific setup for their own safety and the safety of anything else. They will generally try to eat anything they can fit in their mouth (and sometimes things they cannot), and the risk of potential diseases being transmissible between amphibians is well documented. That said, I have safely kept axolotls with snails, ghost shrimp and live plants such as java moss, java fern, green myrio and elodea. Never keep axolotls with fish of any kind, as they will almost invariably pick at the axolotls delicate gills.