I ordered the shorter brackets for the AquaticLife 48" to make the lights closer together, 16" instead of 18" wide to give me some room. Should I keep it as wide as possible or would the little less make any impact? It's actually just an inch each sideAbsolutely you can. There are many very successful tanks out there lit strictly by kessils or leds. Most are lps dominant or a mixed reef with a few sps. When you start getting heavy into sps shading becomes an issue. So you either have to supplement with t5s or get more kessil modules and space them close together.