Waterfalls are notorious for harboring bacteria, I'd personally stay away from them unless you clean them every day and replace filters often. Even then it is relatively risky. I have the same tank, I'll post some picks of what I did with it, might be helpful.
This is the best shot of the overall tank. It is an old pic though. I've since added a cork cave in the back right. I really need to take some new pics lol