I have had an axolotl since 07- he was a baby when I got him. He has not grown as large as other adult axolotl's I have seen. Is this because my tank is too small? Would he start growing again if he were in a bigger tank? I think his tank is 25 gallons, but I dont fill it all the way to the top because I want him to be able to easily swim to the top and gulp air if he wants to.