Yes cut the byssal threads with a razor blade and make sure not to cut/damage the foot. Otherwise you could cut the shell or try and direct a powerhead at the base of the clam to try and get him to detach on its own.
Check this post, looks like most are deep water which would put them at a similar price.
http://www.reefsanctuary.com/forums/saltwater-fish/56833-reef-safe-butterfly-fish.html
Looks good, I like how you have two "islands". Any space to possibly stagger the two so one is a bit more forward that the other for a little less symmetry? JMO.
Hey guys, took a break a few years ago and back again! Picked up a 14 nano and now have a 34 solana and soon to setup 30 shallow cube. Looking forward to seeing all the cool tanks on here and get some inspiration!
Calvin