[Percula9]

You can move to a 250 watt light if your ballast is rated for it. The T-5 reqiures a new fixture. Talk to your LFS. Brighter lights for your system might light shock your corals. Your tank is only a 75 gal system. If your livestock is doing okay, leave well enough alone. From the picture you posted your corals look good. Remember to replace bulbs evey 6-8 mos. Maybe your ballast can take up to 175 watt bulbs, this would be okay for your corals.