What do i do with bamboo?
 

I was bought a rose & bamboo stick in a glass vase in February. I've left the bamboo in the vase on the windowsill where it's since sprouted. I top it up with fresh water every now & then but it's now growing quite big & the water's getting quite slimey. What do i do? It's well rooted in the vase so do i keep it in water or plant it? Any info would be appreciated.