Well, I have used T5's since I started my 240, I have SPS's, a maxima clam and other light demanding corals. IMO you can grow and maintain them under T5's, however I believe they will loose color over time. They just don't seem to make the corals pop with color like I have seen. I have tried many many bulb combinations but results are still the same. That is why I am in the process of changing over to halides.
3 250 watt IceCap ballasts with XM 10K bulbs