The tank with my P waltl in has a sand substrate, although if I were to re-design the tank from scratch again I'd probably go for either bare-bottom or slate, and then have a range of plants in ceramic pots (using organic top-soil) in addition to the plants I mentioned before.
I have some Cynops orientalis in a heavily planted tank that has a bare-bottom.
This, although not as pleasing to the eye, really does make 'house-work' a lot easier.
Their 'poop' can be easily spotted and removed with a turkey baster, and a siphon around at water-change time keeps it nice and clean.
With no substrate, it makes the feeding with things like bloodworms
so much easier.
Having said all that, (and not wishing to complicate things further!), I'm very interested in ;
Walstad method - The Free Freshwater and Saltwater Aquarium Encyclopedia Anyone Can Edit - The Aquarium Wiki having read her book recently......but that'll have to wait until my funds/time allow!
You can't really go wrong with a bare-bottom tank, a few rocks and hides scattered about, and a good handful of healthy plants........sometimes simplicity is the key :happy: