Buying the art is one thing, owning it is another. The days when you just hung it on a wall and forgot about it (looking-after-wise) have long gone. Imagine, for instance, owning something by perfectionist Jeff Koons. His demands for his work are so extreme that the Guggenheim Museum once put off mounting a survey show because finding 'the technology to match Jeff’s vision became impossible.' And then we saw this version of Koons's Three Ball Total Equilibrium Tanks. The three basketballs are intended to be symmetrically suspended in the sodium chloride reagent. The basketballs are at such a specific point of equalibrium with the liquid they are immersed in that even the vibrations from people walking by can affect the balance. The solution has to be changed every time the piece is installed and constantly monitored if the work is to be presented as Koons intended. 'Oh, oh, Jeff’s coming. Get the pump.'