I wouldn't trust a standard container to hold with the weight of the water. I have a 27 gallon heavy duty container from Lowes that works great even for long term storage (6+ months driftwood soaking/temporary aquarium). They are rated for 400lbs, ,so you can actually move them with water inside.
I did use that 50-gallon rubbermaid storage container. I just finished it about an hour ago. I'm glad I didn't read the last post until now that I am done, because it would have worried me. However, it last post is probably correct because the rubbermaid was bowing out on the sides big time. I will post pics of it in my build thread under saltwater reef aquaria later tonight.