You can see some large 180 gal arrowana planted tanks, these are
covered though!
I think Vincent has some photo's. I'll check the link or you can go to
www.aquaticquotient.com and hunt for it.

I've always wanted to do a large school of Whimple piranha(C. mento)
in a planted tank.
I think they are very well suited for a planted tank.

The large reds and blacks often will uproot plants when excited. If
you have only a few of them it's fine but a number of them can do some
damage in packs. Not sure if the whites do that as much. 12" is a big
old fish.

Regards,
Tom Barr