Concerned about a floating axolotl

I have a very young melanoid axolotl (only an inch and a half to two inches, tail included) named Nightmare. I am concerned because he will often float near the surface of his water, sometimes on his side. A previous axolotl of mine also did this and eventually just plain died so I really want to know what is causing this phenomena and what I can do to resolve it. The tank he is in is very small (less than a gallon) and I do at least 60% water changes of dechlorinated water at least every other day and I feed him every day (bloodworms and sometimes very small crickets). I also have an adult leucistic axolotl living in a ten gallon tank next door with a filter, but I don't feel safe putting the two in the same tank until they are much closer in size because I know they often have cannibalistic tendencies for various reasons. Any kind of tips and advice will be much appreciated. Thank you. :]

I do know that its somewhat normal for young axolotls to float. Mine spent quite a bit of time floating, one more than the other. Whats odd is that it floats on its side, whats the water temperature? Is there an air stone? I hope someone with more experience can find a better answer.