If you can get a picture, that would be helpful..
As for gas bubble.. is it in the substrate or the fish? Not quite understanding..
If you can, find out these answers as well:
Size of the tank
Is it heated (what is the temp)
How often and how much (%) is the water cleaned
Is water conditioner used
How much food are they feed, how often and what type of food
Answers to those may lead to what is going on, and could help us help you better.
For now, tell them to do a large (or 100% if no filter on the tank) water change with like-temp water and conditioner.