I keep mine under T-5s so they get lots of light. They get very little flow though and do very well. I've discovered you can grow them almost anywhere but they look their best under med- high lighting and little flow.
They will grow anywhere, but for best color you will want to give them medium indirect or direct light. Under higher light situations the purple becomes more brownish and NGs get a white/tannish color to the middle of them which you can see below:
Mine are on the sand bed, under 150W MH probably about 22" from the light. They grow fast and the purple is a nice deep color. For flow they are in med/high flow. Basically enough so the skirts are constantly moving but not enough as the blow over.
Mine are high in my tank with 250w 20K lights, they are holding their color good and the polyps look great, the down side, they arent putting out any babies. I think I have had one baby in about 4 months. I am thinking of moving them down in the tank, the thing that stops me from doing that is they look healty where they are at. These are them Right center of Pic
The more you feed them the faster they will grow......I used to feed mine every other day and would get 5-6 new polyps a month if not more.....I have mine in med flow direct lighting but on the bottom of the tank....Colors are real nice and they seem to be growing rapidly.
I have mine about 18 inches down in my tank under 250 watt Reeflux 12k's. Flow is variable, but I would consider it "medium". Their colors are really deep purple in that location. They have been growing like weeds for me; I started with 2 polyps in February, and now have more than 30.