I think that's a pretty neat idea. And I think I understand what you mean about your sealing job. Correct me if I'm wrong, but you only want say, half of the spiral chute filled with water so you can see it rushing down, rather than having the bottom half of the machine completely full of water?
You'll have to be very careful about getting your flows right:
- Too much outflow from the tank = flooding of the chute
- Not enough tank outflow = poor filtration
- Too weak of a return pump = overflow of Tupperware container and filling up of the spiral chute
- Too strong return pump = drying up, possibly you'd end up forcing the water halfway up the pipe, then running out of water in the Tupperware container to get it all the way out
And you'd only get one shot at it really, because once you flood the tank and the water starts coming through down to the chute, everything is packed away inside and you won't be able to touch it without making a huge puddle!
I'm not entirely sure about the power head you plan to use. If it's a submersible pump, do they burn out if they pump air instead of water? Because if its too strong you run the risk of that occurring. But at the same time it'd have to be strong enough to provide adequate filtration.
A couple of photos of the chute could be helpful as well!