Depends on your circumstances. Do you have a canopy? If so, retrofit kits are available. You'll need to change out the entire system...although may be able to use your existing ballast. New end caps and bulbs may be all you need to change, oh and reflector. They key to T5s success is individual reflectors or a reflector that's bent "gull wing" shape around each bulb.
Yes, it will be in a canopy... When I get the tank and all I will post some pics of ballast to see what you think if I can just switch over the lights and reflectors