For the crabs, I just grabbed 'em with tweezers or whatever else I could use whenever I saw them. I imagine that might be more difficult with the size tank you have. Eventually I think I managed to get them all.
I bought a Mantis trap. It worked for catching some of the crabs. It's also good for catching fish. It will probably catch your Hawkfish. It catches my Dottyback in about 10 seconds.
I had a Mantis shrimp that came with my LR
. After failing to catch him through other means, I dunked his rock in FW
for about 20-30 minutes. Yeah, yeah, I know it probably killed everything in the rock. I haven't seen the Mantis since.
Keep the pistols. I have one that came with my LR
. I actually see his head peak out fairly often.