How many Tunze turbelle 6000's?

[jmack]

I was looking into replacing my powerheads with the Tunze turbelle streams...just wondering how many I would need for a 120 gallon? The kit for sale at Marine Depot (TS21) has two 6000's plus the controller.http://www.marinedepot.com/md_viewItem.asp?idproduct=TZTS21

 

[techigirl78]

Any other flow on the tank?