You could just experiment with placement. Just try and aim the current from the heads in different directions, and towards different levels to create a somewhat random pattern. Just don't aim any so low in the tank that it tends to kick up any sand. I have also read that having them go all in the same direction is a good thing. You will get a different result from each of the heads depending on where you aim the output. I went that route in my tank, and noticed the best results with my coral. I would say that you should have at least one pointed towards the surface to help break up any film and increase your gas exchange. Just mess around with it. The best placement is where you notice the best response from your inhabitants. I don't think that there are really any "rules" for powerhead placement. As far as the anemone, it will probably wander a bit once you place it in the tank. It will usually find a spot where the current and lighting is to it's liking. I do, however, think that your lighting situation is much too shy for most anemones to do well. Some do not require as much lighting as others, but most require some relatively intense lighting to really do well. I have about 400 watts of pc lighting on my 55, and my bta seems to be doing pretty good. I have only had him for about 8 or 9 months, but so far so good. And to put lighting in perspective, bubble tips do not require as much lighting as many other types to do well. Most will recommend metal halide lighting for keeping anemones because they are best providing the intense lighting that most anemones really require. hth
but also what i'm getting is that you want at least ONE to break the top of the water to help with gas exchange but for some reason I was thining deep ocean little movement was best and I only have one powerhead and it might put out 300 GPH dunno its a powerhead brand and a 402