Fertballs, pssh. I'm yet to see the results. I've used a couple under my stems and there's been no change in growth. Now lighting, that's where it's all at for me.
I'm assuming nothing can be done plant-wise on the 120cm tank, right?
So I'll focus on the 3 footer. I'll need some specs though.
Lights?
Fauna (animals)? How many of them? Can they be moved?
Flora (plants)?
Filter?
What look are you going for?
Have a browse through these and see if you like any of them, even just some of the features they have that you want would be good. http://showcase.aquatic-gardeners.org/2 ... ry=0&vol=1
HTH