The inverted pop bottle trick works like a hot damn for me. Here is a photo of all the parts that you'll need. I use an empty pilsner glass
(works better that way), an elastic band and a 500ml plastic pop bottle. You need to cut the pop bottle to creat a funnel like this.
I also cut two notches in the base of the funnel so that the elastic securely holds it into the pilsner glass like so.
Here is a photo taken with the trap in place. I knew where that bugger was hiding, so I just leaned it against his favorite hiding spot and added some irresistible mysis shrimp for bait.
Sorry about the algae folks, I'm still curing some Vanuatu rock.
The next morning I found somebody happily chewing away on that nice juicy piece of shrimp. He unfortunately knew his fate. Just look at the fear in his eyes.
Fear not fellow reefers, the masked reefer has sympathy for his fellow dark denizens of the night. He has however been banished to the fuge for "behavioural modifications".
Hopefully that helps you out Kristian