I've treated my tank a couple times, I never found my hermits to be affected. Never had any shrimp because of my wrasse. Interceptor will kill any starfish you have as well so get them out of there as well.
I treated my whole tank because I have some colonies that have encrusted on the rock and besides having to chip them off the rock I didn't want to leave anything behind for the bugs to survive on while I treated various colonies and frags. Not to mention I just have too many for that anyways.
As for pod population decline. I did notice some dead pods floating about but didn't notice much of a decrease in population, they were still hanging about in my overflow in pretty good numbers and my wrasse managed to still ferret out many from within the rocks and such.
As for dangers, I have never encountered any. Its business as usual in the tank while you're treating for most of the critters (although the first time I treated there was a lot of nailbiting on my part). At about hour four you can see the redbugs aren't happy campers and start to fall off the corals, about hour 5 you can actually see polyps on corals you didn't see polyps before. By hour 6 I was preparing my big waterchange (which usually took me into hour 7) and running carbon. At about 8 hours the tank looked sooo much better with all polyps fully extended on those corals that were having a rough time previously.
I don't think I've ever treated interceptor with a sandbed, only since I've run my tank BB. You might want to consult with some DSB people
