Water feature questions

1) I want to build a water and it is going to have a very heavy rock for the water to run down, are there any problems with this?

So long as the sump the rock will stand on can support the weight and the stone is supported and secure it should be no problem, providing there is access to the pump (This could be a trap door in the support grille) oh and never  fit a nozzle to the water outlet.