I've had a tiger tail cucumber getting along quite well in my tank for about six months. One unfortunate night, my wife decided to [quite amateurishly] rearrange the tank and drastically spiked the parameters. If that wasn't bad enough, it stressed out the cucumber and he released the toxin they're notorious for and killed just about everything.
I would now like to remove this risk, but I'm afraid of stressing him out in the process. I would like to keep it alive (so I can resell it), but they're nocturnal. I can catch him quite easily at night but I need somewhere to put him. I suppose I'm open to setting up a quarantine tank to be safe, but I'd rather throw the him in my sump until morning. Either way, I don't want it going crazy on the way out. The best I can figure is to scoop him up with a cup and not expose him to air in transit. What can I do to ensure this thing doesn't foul my water again in removing it?