This will sound silly, but you should add visual boundries in the tank. So they dont go fighting. Also there is this really neat site that is the counterpart of this site. Its called
caudata.org
I pop in every now and then. They will be better to assist you on these amphibians. Seeing as alot of people tend to post int he axolotl threads.
Well hope this helps, good luck and great to know people are getting intrested in these fascinating animals.