had to use the inverted bottle trick to catch me leopard wrasse once, I took out every rock in the tank and still couldnt catch her. Just cut the top part off of a 2 liter bottle,Remove the sticker and invert it, throw your blennys favorite food in there and avoid feeding(might be a bit difficult for you though considering blennys eat algae and this one likes your corals, could take him alot longer to get hungry enough to go in.)
Seems like alot of trouble but its super easy and you dont have to keep your eye on the trap as it takes the fish awhile to figure out how to get back out, Wish ida done it before spending 3 days trying to catch the wrasse the old fashioned way