Depends on what T5 set up your using and how tall your willing to stack your liverock to place corals on. you'll be able to keep your typical LPS and softies regardless. If you have a good 4 bulb T5 set up (ice cap retro, TEK, giesemann) you can keep SPS just make sure they are up in the first 18" of your tank (high light SPS no more than a foot down, Monti cap and lower light demanding SPS up to 18" down). If you have a marginal T5 set up (Nova Extreme) you should probably upgrade if you want to keep high demand SPS. 4 bulbs over a 12-13" wide aquarium is status quo (its what fits best over that width), wont change anything on how they penetrate a 30" depth.