125 gallon **need a mentor**

[Madreefer]

Originally Posted by mrhasan

For a 125g, canister will not work

Thats not true at all. Those FX5's are a good filter.
It'll work fine for the mean time. Of course a sump is much better as to reasons already posted.
I recommend that you do not use any of the media that comes with an FX5.
Fill the trays in that filter with lots of rock rubble, don't use the sponges and get some nylon bags and put some good quality carbon in them.
I ran an FX5 on a overstocked fish only tank before which was on a 90G.
I did have a junk Remora skimmer on it though. It was supposed to be a fish only tank but it was also filled with softies and an anemone.
I have since took that tank down as two tanks was just too much work.

[BlueWorldAquatic]

Sump is the better choice. Not only does it allow more water volume, it'll allow a place to hide your equipment so no messy mechanical parts and wires exposed.

Do it now, as yiu will regret it in the future.

[shanks]

Originally Posted by BlueWorldAquatic

Sump is the better choice. Not only does it allow more water volume, it'll allow a place to hide your equipment so no messy mechanical parts and wires exposed.

Do it now, as yiu will regret it in the future.

those sound like wise words actually,

[CM125]

There are a couple different ways you can get a sump. For your first one I recommend buying one over making your own. They are fairly easy to setup and will help you understand how they work, then later if you feel like building one you can. You still havent mentioned if your tank is predrilled, im going to assume no, since you come from FW background. I recommend two overflow boxes, having a back up is always nice, and they will cover more area.

[shanks]

the tank is not predrilled. i suppose this will be someting i will have to consider.

[CM125]

not predrilled is not a big deal if you already have the tank, although predrilled in so much better (can go right against the wall, no noises, no flood risk) Its up to you. There are some very good overflow boxes on the market, and they do give you more space inside the tank.

[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.