If he's not gasping for air or has rapid breathing, he should be ok. I got 2 little clowns a fee weeks ago and they hung out at the top of my tank..on their sides. I touched them on morning to make sure they were alive. Lol! They swim in the rocks now....may just have to get use to their surrounding.
If you want more than one firefish introduce them at the same time. I have two and they have never shown aggression towards each other or any of the other fish. Very peaceful. The both sleep cuddled up next to each other in a cave. They eat anything I put in. I've never seen them jump but when they get scared they dart very fast around so I do have a screen top I keep on my rimless. When I first got them they hung around a cave on the right side of my tank towards the bottom, probably about 4 - 5 months it seemed. Now they move all over the tank, mostly mid to lower level but don't swim back and forth, mostly hover. Good luck, they are great fish.
Thank you. But sorry to let y'all know I had to return him because my purple dottyback hurt him. I returned the dottyback and the firefish blenny. They were both from different stores