I spent this morning out in gorgeous bank holiday friday sunshine converting a manky old algae-covered tank from my Dad's attic into this for the roborovskis:
It took a while to clean it all up properly. I was going to just make a lid but then I got a bit carried away and made a shelf from an unused cork floor tile - I wouldn't consider this for most hamsters, but my two robos have been very uninterested in chewing anything apart from their food, so I think it stands a good chance of surviving. All the wood I've used is untreated and has been sanded and scrubbed.
I've made a sling for the water bottle from a strip of mesh, just need to sand down a few sharp edges on that now, and go back up into the attic to find a ladder from a very old hamster cage that's up there, so the boys can get up to the shelf, and voila. It only cost me a £1 for the mesh, everything else we had.
The idea is to give them much more room to dig in - I'll be putting in a lot of shavings on the bottom layer. As to how big it is - it's 2ft long, I don't know what that is in gallons, my Dad said that US and UK gallons are different too so even if we worked it out from his fish books, it wouldn't be the same as what you would call it over there!