Thanks!

I think I found a good site with the info that I need to learn.

http://www.aquarium-lighting-guide.com/metal-halide

I will check both websites!!
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I am going to hijack my own topic.

Sand Bed or Bare-Bottom Tank???

I think I am going to do BB

What would you guys do? if you have a chance to start a 180 gal RR tank?