Dirt and water setups are probably not the best mix. I think if any substrate it's moss that should be used because it's easier to deal with. You could put a screen over the intake so whatever moss that gets sucked up can easily be removed before it clogs the filter. Dirt is just too fine for you to be able to combat it clogging your system up. I would like to incorporate some kind of land mass for her to use, and I think I'm just going to use the plexi, and moss. I was also thinking maybe reptile carpet?