Artificial light demand depends on the aquarium animals need. Some may need bright light, some dim or vibrant lights. So it totally depends on the animal's requirements. As axolotls eyes vision is very poor and can not tolerate bright light when the owner decorate the tank they should not consider any artificial light for their axolotls. Because axolotls like dark places and there will be a light in the room for which the tank will not be fully dark at all. Also if there are plants and some other creatures artificial light can be added but the light should not be too bright as axolotls hide themselves from bright light. As well as ensure that you keep enough hiding space for them to hide itself from light.