The purple cap is positioned about 6 inches below the water's surface so it gets a pretty good amount of light. Flow on the other hand is moderate. I have other corals blocking a lot of the flow so it does not receive too much direct flow, but this doesn't seem to be too much of a problem. I will be restructuring the entire tank soon and will make this piece and my tort the center pieces of the tank and structure everything else around them. I'm not looking forward to it though as it will be difficult to move the cap without breaking it, but I really have no choice.
