I have mine mounted about a foot above the top water line. While I feel it's adequate I also feel I could use more light. I am hoping for a mini maxi anemone some time in the future and I don;t believe it would be enough light.
Thats just my opinion and experience though. I may be wrong. My corals have perked up quite a bit after adding the mh
instead of two PAR38 LED
's bulbs but I still feel it could be better.
But then again, who is ever happy 100% about their setup? Theres always something you want to be better. LOL