overflow box

[snaggle]

I am looking at setting up my 55 on the same sump as my 20 and 77 I dont have the tank drilled, and I dont want to bring it some where right now. I am looking at getting an over flow box like this.
http://www.jlaquatics.com/cgi-bin/s...alogno=of-cs050
but the guy at bi als told me me I would need to buy a pump for $30 to keep it going if the power went out. Do I rilly need one? is there a better way can I do something to make it so I dont need the pump? and the bottom of the tank has a sticker that says made with tempered glass I dont know if it is the hole tank od not please help me.