Worst thing for me was an unquarantined powder blue tang. I had her in the bag getting drip acclimated on top of the tank. Right when I opened the bag all the way she jumped out of the bag, landed on the tank top of the closed side, and flopped her way in to the tank. Only my foxface has ever jumped that far before. Took me 2 hours to get her back out after I disassembled the rockwork.