Hi Salad,
If you could give us a little more information so we can narrow the field a bit...:happy:
An axolotl will float for a variety of reasons. Water quality issues and gravel impaction are the usual suspects.
Could you please advise of your tank water parameters such as Ammonia (most important), Nitrite, Nitrate, pH and water temperature (very important).
What sort of substrate are you using? (ie. Sand/Gravel/etc).
Is there any water current in the tank?
How large is the tank? Any tank mates?
Has the tank been cycled? If not, how frequently are you doing water changes?
What do you feed your axolotl? Axolotls are messy little grots. Do you spot clean the tank frequently removing wastes and left over food?
Axolotls will also float if they are stressed, if they have gas, if they are constipated and sometimes to make life interesting they will float just for the hell of it.