"Waterworld ©" wrote;

He may not be feeding because he is in fresh water and not brackish.
That's
not fact it's just a possibility that might be worth looking into.

I would suspect it being a very good possibility. When we had the pet shops,
fish that prefer brackish water, were kept in brackish water tanks. If that
were the case with your Bumble Bee Goby, comming out of a salt tank, to a
salt free one, might have trigered a hunger strike........ Frank