How to place T5 light fixture over your tank?

I wouldn't touch the divider. Could end up cracking it in which case you will structurally weaken the tank and you could blow out the front or back.

You really don't have a lot of room there. Even if you could get a Tek fixture in there you won't have a way for the heat to get out of the fixture.

You could consider using a 24" T5 fixture on the right side and keeping your existing fixture on the left. This would maybe allow you to add some corals on the right side.

Nice looking tank by the way.

 

I don't know if it's possible, and Im sure you have already thought of it, but could you just take the top trim off and cut the drywall/studs so that you have more room? Also, as you have already cut the middle dividing wall, why just cut it more so that you have more room to work with? Instead of trying to cram a light fixture in there, make more room for your self.

 

I like this idea although I think there should be just enough room to do the same on the other side too. About how many watts of T5 light should I shop around for?

 

I would look for a fixture with as many bulbs as would fit. If you get a fixture with individual reflectors you can normayy get 6 bulbs on a 55 gal tank. It looks like you can't use the full with of your tank because of the room wall. You might only be able to get 4.

 

IMO cut a chunk out of wall going across and hang the lights from the celing (you would need to be able to take the light down when you do your matinace. keep that in mind if you hang the light quick disconcet or something) and just have it run the lenght of the tank.