mars Auqua 65 how far off water

[bowhunterj]

how far off the water should a mars Auqua 65 be? I have them 12 " off now but feel they should be higher , i'm running 50% blue and 10% white still see some bleaching.

 

[bowhunterj]

oh, 90 gl 24" deep

 

[bowhunterj]

that's a 165 watt I use 2 of those