You could try a fish catcher. It's basically a pop bottle with the top cut off and flip around back into the bottle. Google pop fish catcher and I'm sure you'll find it. Also you could try not feeding them of a couple days. I tried everything with a damsel once in my 125 gal
reef with like 200 pounds of live rock. And I ended up having to pull out all the rock and drain the tank down to like 20 gal
left it was a long day. Best of luck.