Sorry to hear that. I love tusk fish and wanted one for a long time. I had a baby 1-2" tusk fish that was doing great in my tank for months until I had the opposite of your problem happen. I added a mystery wrasse 2-3" (only slightly bigger then the tusk fish) and the mystery wrasse killed the tusk fish!
My 230g fowlr tank would be a good aggressive match but Doug told me, no more fish for that tank, as he thinks the big guys will most likely kill any new ones. It is getting full, there are 10 fish in there and 3 are huge and a couple more will get big. When it comes to adding though I find it depends on the fish, the burr puffer (which I thought would be ok) didn't work out (oddly the eel and hawkfish terrorized him) but the filefish (that I wanted for aiptasia control, but thought the trigger might kill) is totally fine in the tank. However if there was ever a fish I'd try to sneak/squeeze in, it would be a tusk fish.