Chinese algae eater is sick?

[mmjb333]

This morning I woke up and checked on my fish, I have a chinese algae eater in a 20 gal well circulated tank, with 2 tin foil barb, a paradise gourami and a tiger barb, he has always been shy and moves quick when other fish come near, but when I just checked on him I thought he was dead but when I looked closer I could see that his mouth was moving still, I moved him to a smaller 1 gal tank we have to acclimate new fish or kinda as a hospital, I don't know what is wrong with him so I haven't done anything yet. He doesn't move, and whatever side he lands on he stays, when I turned on the filter for the small tank the current flopped him around a little bit but he didnt even react, he is now laying on his side on the far side if the tank away from the filter, I added a price of spinich and weighed it down with a rock and put it close to him so he could eat, but I have no idea what is wrong with him, I checked the levels of the big tank and they were all good, and he was fine yesterday. (I know this is long but I want to give as much detail as possible)