If the rim is 2 inches or more all the way around, then he probably won't get out. They get out by sliding up the side.
If the smallest hole in the powerhead is 8mm across (diameter), then he should not be able to get into it.
Quarantine is hard, because he will get out of it. I would just put him in.
Of course, you must first have a pipe for him to live in. The pipe must be longer than he is. I would lay the outlets of the pipe sideways so that waste and sand will not pile up inside it. And you should be able to reach the outlets with a feeding stick.