My 180 is a marineland and has the black cross bracing. Daniel recommended 3 which is what I had thought would fit. I'm going mix but will probably be lps dom. He also recommended depending on mounting (canopy) 120° but if it's 12+ 90°. I'm thinking about cutting holes in the canopy and mounting the light on topkind of recessed into the top from the outside. Canopy is in "storage" currently so need to get it out. I think it's 10-11" from water to top inside.I put 4 on my 180 but used the 90 reflectors and will be an acro dominant tank.