My normal BTA will consitently move to meet the following criteria...
1) Foot underneath a rock. It needs one with a decent amount of space (tunnel) so the body can extend out.
2) Low to moderate current, but more on the low side. This contradicts most of what I have read, but he goes where he wants and he doesn't read books or the web.
3) medium light. I have 4x96 watt PC's over a 65 (3 foot lights over 3 foot tank) and he will not stay in the top half of the tank, and is currently about 16" down, 8" up from the bottom.
Once there he will stay for years, until I repossition the rocks or try and relocate him. A number of attempts to give it more light and more flow have not only failed, but also left a few corals in his way back down dead or badly stung.
I strongly advise putting foam blocks over any powerhead or pump intakes for a couple days until it settles down. Mine got chewed up the first night in the tanks but luckily recovered.