Hanging 60" light on 72" tank?

[golftall]

My wife, the aquarist, wants to upgrade to a combo light unit on her 180 reef tank. As this job falls to me, her aquarium lackey, I'm looking at options. Should you always put a 72" light over a 72" tank? I was wondering if a 60" would work as I will hang it, thus no supports to worry about. That would reduce the MH lights from 3 to 2 (250W) and put the actinics about 9 inches from each side of the tank. The wattage goes down a good bit, but would still have almost 800W for a 180g tank.

Thoughts? And thanks in advance for your insight!

Charles

 

[ltljoker]

if you go with 60" lights on a 72" tank you will have shadows on each end of the tank due to lights not reaching the end of the tank. :frustrat:

 

[Bifferwine]

It's doable. My 240 gallon tank was 7 feet long and I used a 6 foot long light fixture over it. The ends of the tank were darker, so I just put lower light corals in those areas.

 

[Reefrookie]

I read somewhere that you should use a slightly shorter light when hanging it over the tank. The same length light as the tank will shine on the floor around the tank instead of all the light going in the tank. Don't know if this is correct, but it sounds about right!

 

[golftall]

Thanks all - appreciate the feedback. Found a great deal on a 72" light, so went with that.

 

[dcantucson]

It also depends on the fixture. In my combo MH/T5 the T5 lamps do not extend all the way down to the end of the fixture. They start at about 6" in from the end. So although my lighting unit is the perfect length I still have shadows on the ends of my tank and that sucks.