I loss my Antennata Lion yesterday. I asked the experts at 2 of my LFS and even took samples of my water for them to test and neither store could figure out why. My water was good the nitrates were a little high (40ppm) but not enough to kill. He was fine for the most part, didn't eat for like 2 days came home on the 3rd day and he was swimming upside down next to my intake, he stayed there for a while, then floated upside down to the top of the tank, 30 seconds later he swam down to his favorite rock and sat there for like 10-15 min then floated back up to the top. I took him out and put him a holding tank with the same water from the main tank, he died after about half an hour. 
I've had a guy offer me his 2-3" Undulate for $20 and I've been considering getting it to go in my 75 with my Chainlink Moray, Yellowtail Damsels, Maroon Clown, and Spotted Hawk. I've been reading on how aggressive these guys are though and IDK if I want to risk my moray, clown, or hawk. I figured he'll eventually have at the damsels which I don't mind but I don't want him killing anything else. Think it's a good idea?
I've had a guy offer me his 2-3" Undulate for $20 and I've been considering getting it to go in my 75 with my Chainlink Moray, Yellowtail Damsels, Maroon Clown, and Spotted Hawk. I've been reading on how aggressive these guys are though and IDK if I want to risk my moray, clown, or hawk. I figured he'll eventually have at the damsels which I don't mind but I don't want him killing anything else. Think it's a good idea?