One-Spot's are smaller (maxing out at about 7", but most stay around 5-6") and are fine for a 75 gallon+ tank
http://www.liveaquaria.com/product/prod_display.cfm?c=15+1465+2704&pcatid=2704
The more common Foxface Lo will definitely be cramped in anything less than 6' when full grown, though!
I've heard that Yellow Tangs, if added prior to a Foxface, will bully the crap out of them. Oddly enough though, I've heard that if the Foxface was there first (and well established) it will become BFFs with a Yellow Tang :fun4: