If you wish to repot the plant just move it up to a slightly larger container without disturbing the roots as much as possible. Use a well drained peat based mix and do not over pot for the best growth and flowering. Be careful while repotting as the stems can be brittle and snap with too much rough handling. If any of the stems break off they can be easily rooted to make new plants and you can propagate more of your heirloom cactus. Attempting to repot is entirely up to you if you are nervous about the process there are great tutorials online on how to repot a houseplant that you can watch and learn how to approach the process with knowledge and without fear.

You can check out more repotting and care tips here.

Courtesy of the NYBG Plant Information Service