First, let me first commend for being on the right track; it is always good to do find out details prior to obtaining a pet. Second, to keep axolotls, this is the basic idea:
(1) Axoltols need lots of floorspace, depending on their size, so you should measure your tank. Axolotls need this space for "alone time" from one another. You should be able to roughly gauge this by looking at your tank and from the size of the animals.
(2) Do not crowd axolotls that are under 3" together, as they are not usually over their cannibalistic stage at that size.
(3) A filter that is reasonably powerful is probably required (though not essential). I personally use a Fluval 2 for my 5 axolotls of assorted size (between 3.5" and 7"
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(4) Axolotls prefer live food, but will also take other types of food (e.g. salmon pellets). I feed mine a combination of blackworms (a relative of the earthworm) and redworms (a type of earthworm).
I hope this information helps you. Cheers.