If I did it all over again I would have stuck to just one nem in my 90.
When I first started I had no idea how big they get and the problems with keeping them from touching corals(especially if they move on you)
Now I had to get a 180 to accomidate the both of them.
I'm not sure how big BTA's get, but just something to keep in mind.
Also, when you have a clown or two being hosted in one you're probably going to be tempted to get something for the other nem, which rarely works out unless you're tank is HUGE