This was my first proper experiment utilising "over-driven" T5 lighting to try to achieve more than is possible with metal halide lighting. It's obvious that as metal halide is a spotlight that it's intensity is lost the further from the light you get in any direction. T5s are less intense only because they emit over a wider area.

The beauty of T5s is that they can be rammed into a small space very effectively, and each T5's emissions will add to the one next to it. The outcome of this is that while light intensity in the first 1-2" will not be as high as a halide, it will punch much deeper as the light from the tubes overlap each other more the deeper into the tank. To overcome the drawback in the top of the tank, I used ballast from the US that can be overdriven... my 39w T5s were running at 80w each!

To try to achieve the high PAR ratings that halides have at the surface, but over a much wider area, I built a custom hood to keep the tubes just 1CM above the water surface. Circulation in the system was high, but not aimed at the surface to avoid splashing the bulbs.