New floating problem! :(

[Caileighferg]

Last night I noticed my little albino floating under his hide... I lifted it to see and he swam to the bottom but kept floating back up and scurrying to get under anything he could. I’ve read that this could be due to gas build-up or air bubbles. As of now, I have him moved into a plastic tupperware tub with the water level just above him. He ate a couple sinking salmon pellets and a few frozen bloodworms just fine. Any recommendations or ideas on what this could be?