I had two rotastaks joined together for our hammie, as one wasn't spacious enough. You can get extra tubes, try ebay or online pet stores. Personally i found mine to hard to clean & they are being sold on facebook next week. He now has a new cage, made by pennine, it has tubes but not as many and the actual cage is much more spacious x
We have the large rotastack space command centre for our syrian and some of the connectors on the tubes are splitting. Does any one know if I can buy some new ones somewhere? It is the little red connector rings. I have looked on ebay and other places. Can't seem to find any single or packs of just the rings anywhere. There are tube packs for £10 but theese look like they only come with 4 rings.