Well, I don't know much about axolotis, but from the brief bit I just read, they're very messy. Are you already well familiar with axolotis? Are they messy like turtles, with large, floating poop problems, or messy like carnivores that drop lots of thier food?
Large solid waste is best handled with a waterline drain and sump setup, with the drain leading to a screen you can easily clean the waste off of on a regular basis.
Lots of food waste or liquid waste, would best be handled by a wet/dry or a canister filter one size rating above what is normally recomended for your tank size. (Axolotis are not sensitive to high current, are they?)