Oh the irony. It makes sense to put a BTA in first so it can pick out the best spot, but it will likely die unless your tank is matured somewhat.
Using logical thought process:
If 1) Nem should go in before coral
and 2) Nem should not go in until tank has matured somewhat
then 3) Coral should _also_ not go in until tank has matured somewhat, even if they wouldn't have a problem otherwise
I have kept both a carpet nem and a White BTA. The carpet died (put it in when the tank had only been cycled for two months), the BTA is thriving after two weeks in the DT. Tentacles are nice thick and bubbly, mouth closed. My only issue is he moves every night after the lights go out (no I did not put my lights on an acclimation program when I introduced the BTA, but the lights are not overly intense to begin with). While I understand that BTA's are known for being relatively mobile compared to other nems, moving to a new spot every single night seems a bit excessive. I'm not overly worried about his health since his mouth is closed and tentacles are full & bubbly, but it would appear that he's not done getting the lay of the land and I'm learning a lot about his preferences as I go.
I have _read_ that BTA's like both high light and high flow.
I have _experienced_ that they like low light and high flow.
It is too soon to tell if the sensitivity to light is part of the acclimation process. It's been two weeks since he was put in the DT, maybe he's still settling in. But he has moved every single night after the lights have gone out, settling in a different place each time. I will say that the past few days he's been settling in places with slightly higher light. I don't know if he's starting to prefer that, or if he's just been unlucky lately in choosing spots because he only moves when the lights are off and has no way of knowing if he's settled in a bright or shady spot until the next morning.
Either way, the behavior I have no doubt about is that he definitely prefers rock to sand (unlike the carpet nem) and his favorite spots are places where the foot can really get wedged in deeply. It's almost as if, if his foot is exposed to any light or flow whatsoever, he will not be entirely satisfied with the spot. He seems to want the foot completely protected from anything/everything, while wanting to keep the oral disk/tentacles exposed out in the light/flow. That certainly makes logical sense from an evolutionary perspective.
I mention all of this as a way of suggesting that your preferred area for the BTA might not work, at least not initially (because it is very exposed to light and there is not a deep crevice to entice it), and to emphasize just how protective BTAs are of their foot. This has all been a revelation over the last two weeks as I try to help the BTA find his happy place. IME, providing the perfect crevice (one where the foot can completely fill up the crevice with no "backdoor" that light or flow or fish can reach) is critical for getting the BTA to settle where you want it. And even if you do provide that crevice, the BTA might not take to it at first because he may be especially sensitive to light or just unsettled/mobile in general.
I just wish I could tell you if my experience is how BTAs regularly behave or if this is all symptomatic of a BTA that simply hasn't fully acclimated. Something to keep in mind as you go down this similar path.
