Welcome Veeran! 120g tank is a great tank to start off with! Personally, I would say that you would need 2 rubbermaid tote's, but 1 may work if your stocking level isn't too high.
Do you have a picture of your tank?
If you are up for it, we have a section that allows everyone to follow your progress of your tank/build. Here's the link:
http://forum.simplydiscus.com/forumd...-Tank-Journals