If you have your mind maid up on the fx5 no reason to try and change your mind on that. A bad ass filter and more then safficent for a 125. Buy from some one on ebay with a good rating. And you can get them full of media on there to for good prices. Deffenitly look for one with media included because if it doesnt say media included it isnt. And the bio media to fill them up isnt cheap.