[Myka]

I also suggest you drill the tank for a sump. My reasoning is to hide the equipment, but also because in-sump skimmers tend to be cheaper and better quality than hang-on. You can get drill bits from Princess Auto that actually work quite well and are cheap. Practice on an old 10 gallon tank. Use some sort of guide like use a hole saw in a piece of plywood, then tape it to the tank. The glass on a 10 is really thin and they break very easily. So if you can drill a 10 you can easily drill a 125. My personal rule of thumb is whatever the size of the hole, I don't go any closer than that to the edges. If you decide to bottom drill, check the tank manufacturer, some temper the bottoms and you can't drill tempered glass (it will shatter). Look online for how-to's for drilling and installing and overflow. I recommend a Herbie style drain, and because of the length of your tank I would suggest at least a partial coast to coast overflow because Herbie style drains are better used on single overflows, not dual.

I am also not a fan of using canister filters on reef tanks, especially large reef tanks. If you do use it though, do as "madreefer" suggests regarding what to put in it. Expect to have to clean it once a week at least or you are likely to end up fighting high nitrate issues (read: algae). For what the FX5 can do (polyster media, carbon, and GFO) you can easily achieve in a sump where maintenance is much, much easier.