I was wondering what most people prefer. The 4' x 2' or 5' x 18". I'm sure it depends on the type of fish you get, but does it really make that big of a difference? Which size is more common? If people could tell me which version of a 120 they have, along with the inahbitants, that'd greatly help me out in deciding which one to get. And ofcourse, pictures would be great 

