LionFish says......
Yep, Boxfish are rather tricky species to keep alive and well. That toxin is lethal to other fish and well, just about anything else in the tank. I had a guy tell me that his whole $3000 tank with killed by the toxin exuded by his Boxfish.My advice to most people is just not to get them if they are worried about the toxin. You had better keep good wtare quality and make sure those other fish don't harass it or it could be a disaster. Just a fair warning though. Your Cowfish can do it too. So you gota big mess if anything ever happens. However, all the fish you have in there are very docile for the most part and coexist well together so no real worries there. Just keep good tank paramaters and all will work out fine.