I clean my frog's water dish by sucking out the water with one of those curved syringes you get from the dentist when they pull your wisdom teeth out :]
Awesome vivarium- everything looks nice, and soft for the critter bellies~
In my vivarium I use nothing but large wood chips, sphagum moss, river rocks, cork bark, and silk leaves/ plants. To get it all clean I built myself a chicken wire screen that's stapled to a sturdy 2X4 frame. When I'm ready to clean everything I pull the frogs out, dump the entire tank onto the screen, take it outside, and scrub/hose the hell out of it. Comes out smelling fresh, and clean.
Not sure if you would want to do that to your substrate, but it's an idea :]