Solar or gravity powered tank filtration

Anything like this exist, or any ideas for creating something? I didn't find much on the interwebs about it so now I ask you

I'm wondering if it's possible to get enough flow to overcome gravity just by convection, or if this is some sort of physics-defying pipe dream. Of course the next immediate problem is how to regulate and dissipate the heat once the water has moved through the filter... I'm starting to think something like this won't work. At least not for a fish tank

The alternative is to use solar cells to create electricity and power a pump, but those are horribly inefficient and it's been done, probably.

Any other concepts on a filtration system powered by the sun?

How about gravity-powered like this lamp? Would it take too much current to be feasible?

I would be interested in solar if it was efficient.  The gravity generator reminds me of an old clock my grandparents had. I suppose it would work in the same respect if one could figure out a way to only have to reset it once a day. However, this wouldn't work well if u in had to leave town for a few days. I bet it's doable though with today's technology.  

I probably would have my whole house hook up to alternative energy if I could afford the  cost of setting it up.

Cool video, gets the mind thinking!

Yeah ever since I saw it I have thought about powering stuff through gravitational potential energy- I suppose it works on the same principle as hydroelectric but on a human scale. I think it would be really cool if someone designed a pump that could work on the concept, but like you mentioned, it would have to work for at least a few hours to be feasible.

I guess considering the need for consistent power in an aquarium setting, neither of these concepts would work great.

Although I just gave myself an idea, and now I wish I lived near a stream; it would be more than feasible to run a pelton wheel to create enough electricity for pumps and such, and then you could use gravity for water changes as well. When I buy property at some time in my life, I now want it to be near a nice steep stream haha