pirahna (or other messy eaters) and substrate

Hi All,

I'm looking into getting a few pirahnas - I am now doing preliminary
research. It is a very messy fish and I know that with fish that need very
clean water, some folks go bare bottom, i.e. no gravel. But I have heard of
folks doing this and the pirahna run into the bottom of the tank - I expect
it is because of the reflective quality of glass. I have (real) slate
tiles - the square ones you can use for flooring. two of these tiles fit in
the bottom of the tank I was thinking of using. There is like an extra inch
between them (or on one side). I thought to use these and fill the gap with
black sand (you know, like how paver stones are sometimes set). I would
decorate the tank with bogwood and a couple rocks and maybe some fake or
floating plants.

Do you think this is a good idea for easing maintenance of this tank? Is
there anything I should be aware of with this or does this sound like a
viable substrate alternative? Would this be easier to clean?

Thanks!
Jen