It really depends on what type of coral you want to keep.
I run T5HO, but my tank is mostly LPS
dominated. And I am required to replace my bulbs yearly.
There are Power Compact fluorescents, which are similar to T5, but create a little more heat and a little less light.
An older tried and true light is Metal Halide for mostly SPS
dominated tanks, but they create a lot of heat, and bulbs are expensive and also require replacement yearly.
The new breed of light is LED
. Less heat, no replacement ( virtually, 10 year life), but almost too powerful for LPS
, unless you acclimate very carefully. And can be quite pricey, for the better ones. There are cheaper options for LED
, which I've seen good results from in pictures, but for the most part, the jury's still out on LED
If given the choice, and money wasn't a concern, I would go with Ecotech Radion LED
's, or Al sol LED
's. This would allow me to grow ANY coral I wanted, but for my set-up, this would run me about 1500-1800 bucks!
Hope this helps.