See if you can find a 70w halide setup. I am not sure if anybody makes one anymore that is not Chinese crap. These might be long gone. I got a 70w JBJ clamp on at a LFS used section for $20 a few years ago and used it for a while over a 15g with good success... stayed cool and was low energy. They are around, just hard to find. I do not think that Hamilton has them anymore, but might be worth a call or email.
150w Halides are great for small tanks, but there is a point when the tank is too small. You will have to have a fan for some heat, but if you can deal with that, then it should work well. It will be a lot of light for a tank like that. I used a 150w over a 29 biocube and had no heat issues, but this might be 2x more volume than the tank in that photo.
