Sure its GOOD but if you're really serious about adding plants and SET IT UP and forget it then DIRT is the way to go.
Since the fish are in another tank you're good to go.
You might need 3 bag of Miracle Grow Organic, let is all soak for a couple of day. 2 bags of (50lbs) Black Diamond (black) Sand.
I load the back wall with either Jungle Val or Italian Vals. Get 2 large pieces of driftwood (which will help the TEA look) Load it up with Hardy plants like
Anubias
crinum calamistratum (which does require a little more light)
banana plants and or Tiger lotus.
Now this is a piranhas tank, so is it COOL with your arms in the tank from time to time.
ALSO this will need to setup for about a month before you add fish. But once the numbers comes down your good to go. Here is a link to my dirted album
http://www.plantedtank.net/forums/members/jasong75-albums-75-planted-community.html