Hi,
I am planning to start a second aquarium (20 or 30G long), designed to
be planted from the start (my current one has plants but substrate is
bad).
I've been reading up on planted tank techniques and recommendations, but
I have a few questions in regards to maintenance.

I'm leaning towards a fluorite base with a topping of Onyx sand or Black
Tahitian Moon sand. When you have a sand topping like that, how do you
clean the substrate? Can you vacuum like you do with gravel? Or do you
just have to be sure you never over feed :-0. Does waste breakdown
better/faster in a planted tank?
Is there any future maintenance that will be needed, like replacing the
topping or reworking the substrate in general?
I've seen some recommendations to slope the substrate so it is lower in
the front, is there a particular reason for this?

Thanks,
Tom