lock jaw

I had a porcupine puffer a long time ago and I suspected that he got lock jaw before he died. He used to eat a plethora of food krill, shrimp, clams, and even squid. I thought about getting another puffer in the future but what can I do to prevent lock jaw from happening again?

I recently purchased (2 weeks ago) 5 pre quarantine Anthias. 4 of the 5 swim together and look normal. But the 5th hides out by himself and always has his mouth wide open. I read this is common with Anthias, but wondering if it could be something else as well. It’s hard to tell, but I think...