Hello Viccky, from Ruckus ZD point of view you can take a look at few knobs for monitoring:
On Dashboard - add widget - Most Active Client Devices which will tell you the MAC Address, IP Address, User's Usage. this is more of post mortem rather that pro-active measure from my point of view.
then you got: Usage Summary which tells you Bytes Transmitted in last 1 hr and 24 hr which could tell the tale or change in normal trend.
Where to find this - see the URL -
http://prntscr.com/3lrf3p
I have NOT used any program or tool however there are quite a few out there. try Solar wind Real-Time Bandwidth Monitor at
http://www.solarwinds.com/products/fr...
i hope this help.