External Fuge in cube

So, for helping out a friend tear down and move some tanks, he had this leftover. I said, fuge eh... He was using it for a skimmer section. He said, you want it, you can have it for helping.

I'd like to add a big cheato section or chaeto and rock/sand/???

First off, I don't have the slightest idea on how I'm going to add this:


to this:


I am thinking about adding an external reeflo snapper/dart pump. That I am thinking of making my return and having my uv, GFO, Carbon run off of the reeflo, and possibly the fuge... I don't know.

I'm open to any and all ideas, I'm barely good with getting this far! haha! I'm just not a master handyman...

thanks!