Illness/Sickness: Juvenile axolotl floating partly on side...

I have a 10 gallon tank, no substrate, 2 small hides, and some floating fake plants. It has a very low power filter and the temperature stays around 65 Fahrenheit.

I have 2 axolotls in the tank, both are juvenile around 4 inches long. They eat live earthworms and sometimes frozen bloodworms when I can't find any earthworms. They were separated by a tank divider for almost a month, until 2 days ago, so for about 2 full days they were together in the tank with no divider. Before I took the divider out I did a water change and also changed the filter media.

Just a few hours ago I noticed my leucistic juvenile was at the top of the tank floating on his/her side. It is not completely sideways, just sort of tilted with the left side closest to the water surface and the right side tilted down. I did try giving him/her a worm and it took it and ate it. It tried to swim to the bottom of the tank but couldn't seem to stay down.

I put him/her in a container long enough to stretch out fully, but shallow enough to not stress them out. They are now in the fridge, which sits around 5 Celsius, and have put a black wrap around it so the light doesn't stress them out.

Is this just an air bubble? The other wild type juvenile that was in the tank too seems fine, and always has been. I only got the leucistic about a month ago and he/she seemed healthy and fine until I took the tank divider out.

Sounds like some trapped air.

I would have advised to put in fridge but you are ahead of me

Keep an eye on him/her and hopefully he'll be fine after a little while in there.

Mel

I have two about the same size as yours. One of them seems to like "attacking" the air bubbles from my bubble wand and then spend hours floating around full of air. He comes down eventually and has never shown any signs of stress.
Honestly, if his water is clean, cold and he looks healthy, I wouldn't worry, I think it's just something some of them do. Could be a juvie thing?

Thanks for the replies! I had him/her in the fridge overnight for about 12 hours, when I got up I checked and saw they threw up a worm! Seemed fine after that so I put her beside the tank and went to work for 8 hours and let the water temperature gradually go back up. When I got home from work I put him/her back into their regular tank and all seemed well. Just checked on both of them to feed and noticed the same juvenile was floating again! I fed him/her 2 small worms and they went back in the fridge. Probably will leave in for longer this time!

I just woke up to my WT doing that this morning! I was in a rush to get out and do stuff so I couldn't put him in the fridge but I came home to him sitting fine on the bottom, the leucistic might have been floating a bit, but it's hard to tell since they're so active. I figured they needed to be fed so I put a cube of frozen blood worms in and they're occupied enough to stay down now. If they start floating again they're going in the fridge, I'm going to turn the temperature down in here though as I can tell it's a little on the warm side.