The fans are connected in series to a single header on the main circuit board. You can not do a tool-less (or even splice-free) replacement of the fans.

The fans are connected to one another, and to the circuit board via a path under the "deck" (actually above, when right-side-up.) There are cable ties way underneath, and to get to that, you would need to disconnect almost everything else on the cube, including the pump and all of the circuit boards.