Here's the idea:

I have a 4'x2'x2' tank, idea being in the central 40cm section of the tank, there's a reservoir for the waterfall. There should be sides that slant into the centre from the sides where the stream will end(starting from the centre where the waterfall will be, no water in the sides, just solid dry material)

Filtering I'm not sure how it would be done, maybe at least a biological filter and mechanical filter at the sides, looked into internal power filters in aquariums but they have to be fully immersed in water.

Any ideas how to go about doing this? I'd have thought egg crate with some pvc lining on top of it, but egg crate isn't exactly readily available here.

Thanks

RP1