I wanted to get luecs and im tring to decide how many. I was thinking a pair but i noticed that alot of people get three instead of two, is there a reason other than most people sell 3 for $100 which is a nice even number. Any insite would be very helpfull. Furthermore, my tank is a 25 Extra high which is pretty much just two 10 gal on top of eachother. Is it ok to put three luecs in there?