90 gal

[EastBay]

I think T5 would be overkill. The main reason to use it would be for growing plants/corals (in saltwater tanks). Many people just use shop lights, although you can always find something nicer, but still relatively inexpensive.
Personally, I don't even keep a light on my 90g mbuna tank. It sits under a window and gets natural lighting throughout the day.
Really, the lighting is more for the owners than the fish, anyway.

 

[EastBay]

Let me re-phrase that: T5 is not necessarily overkill, depending on how many bulb-fixture you get.
I still say you can spend less and still get the desired results.