Bloating is usually from blockage or swim bladder problems. It can be caused from fighting, foods or possibley injured itself darting about the tank. If it's swimming patterns are still coherent, then I would suspect blockage as the cause. If so, enticing it to eat will be important. Using some softened peas slightly mashed with brine and mabye a drop or two of garlic, see if you can get the angel to eat. Might take a few days but if it consumes the peas, it should clear the blockage.
If it eats the peas and it does not clear the problem, you may need to treat with an anti-biotic. It is not always clear what causes these issues and meds are not always effective. A seperate QT
will be needed if you need to treat. Nitrofurazone at 30 mg
for 3 days. Make sure you try the pea mixture first. If it's simple blockage, the med will have no effect and there is a good chance of making things worse if you need to catch the fish.
What is the main food source for your fish?