Magnifica will seek highest point in the tank to get the most light and current. I think it is impossible to provide too much light for Magnifica and Gigantea (with in reason of course) I have had Magnifica settle right under my 400 W MH. The tentacles only several inches under the water and the bulb is about 6 inches above. It is important that the rock where you want to place the anemone have a somewhat fat surface and big enough for the foot of the anemone, and the anemone should be in a large enough area where it does not touch the side of the tank. If the circulation is poor or light is low, Magnifica have been know to release it's foot and float with the current trying to reach a better place. Needless to say, this would be disasterous in a reef tank. I have had good luck with keeping magnifica under 150 W double end magnifica or higher. I have not try to keep them in lower light than this.
For current, I often use two PH pointing direct at each other meet just above the Magnifica. Sometime I point the PH a little upward This provide reasonable current. I have some picture shomewhere about a 30 g cube tank I keep a smal magnifica in a few years ago. If I find it, I will post these pictures.