That’s a bit close to the water line, you might have issues with hot spots, you’ll know if you see any coral bleaching. My fixture is hung about 15” above the tank, and I’m running 10% white, red, green, and 50% blues and purple. I set it and left it at that, it took my coral several months to acclimate to the change in fixtures, but it turned out well. I run my blue 1% at night, and completely off between 6-10am.