When you are changing the water out look at the roots to determine if they are becoming “root bound”.  If the roots appear to be knotted and formed into a pot-shaped mass then it is time to find a bigger pot or you can trim the roots back a bit. If you choose to re-pot all you need is a larger ceramic or glass pot.  Dump out the rocks, remove the plant and place it into the new pot.  Add rocks and fresh room temperature water and you’re done!