i use the coralife fixture with fans built in, the only problem I have is salt creep getting inside the fans, if the salt builds up the fans make a loud buzzing sound. Other than keeping the fans clean I haven`t had any problems.
I have a 48in coralife aqualight on my 55 and I love it!! I like it so much that I bought a 24incher for my 37 (I will probably add another on it too). I have never had any problem with the fans and it has been set up on my 55 for about 9 months or so. I strongly recommend getting one, and if you decide you don't like it, tell me and I will buy it!!
I have a 24 incher on my 20. For the price online it doesn't get any better. Very bright on my tank. It is suggested you have a cover on your tank though. I use mine with a glass cover. So far so good as far as the corals go....