My axolottle is about 7 years old and he has not been as active or feeding as usual. We have just come out of winter and the weather has become quite warm so I am trying a frozen water bottle in the water. We have been away for about a week and when we came back he has blown up like a balloon. He is so fat. His back legs are about 1 cm wide, he looks obese. His tail and gills are ok. I cleaned his tank before we left and after we came back. I have always kept it regularly clean. He is swimming to the top and taking large gulps quite regularly which is not normal. The tank has large pebbles in it, too large for him to swallow. I have already been though that problem of him eating fine gravel years ago when I got him. His tank is 60cm x 30cm, He has an artifical log he can crawl into, a filter and plants. Can anyone help?