If you notice the gills and tailfin start receding significantly, I would suggest lowering the water level and put a sloping land area in the tank. If its gills and tailfin are almost gone, and you notice it on the land area, then change the terrarium to completely terrestrial and take care of it like a tiger salamander. If this happens you will be one of the few people in the world to possess an axolotl with a genetic mutation to causes it to morph like other salamanders, instead of remaining neotenic.