Thought I'd toss out an update. I had the old one in the sump for about 4 days and then put him in with new new one in the DT. They were fine for about an hour, then slight slight aggression started, but since the new one was in there alone for a few days (still never noticed the BTA) he did his twitch dance a few times and the aggression seemed to stop. They would both do the territorial twitch here or there for the next few hours. After that, the old one found his BTA and was happy. They have both been completely fine together since. The new one sleeps somewhere else and the old one gets his BTA. They'll swim together nicely here or there, but about half of the time they are separate. Seems like it all worked out pretty good. Too bad they wont pair up and host together, at least not yet, but at least they are completely fine together now.