Power generation using the potential energy stored in our tanks?

[Blom]

I am in the process of trying to design my next tank/fish room. Me and autocad have been fighting each other over possible layouts and what not. Trouble is I have no idea on the room I will have to do this as I still have to find and purchase a house. So I have decided to lay off the whole design for now until I have more info on the house. That being said I have found a whole new topic to waste free time on. This topic was poised by a friend of mine. He thought it would be a neat idea to try and see if you could design a tank to be as energy conciseness as possible. His idea was to try and use a combination of solar and potential energy stored in the tank to power the entire setup.

I thought this to be an interesting topic so we talked a bunch about it. Overall the end issue becomes cost. In addition to the cost of the tank setup which we all know to be costly, the added costs of turning the input energy needed to 0 is more than I would like to fork out. I did not do a cost benefit analysis to get a rough idea in savings in cost as it just becomes to complicated for a free time project (I have many projects for marks in school right now). That being said it did peak my interest in using it as a battery backup.

Idea:
Use small turbines to produce electricity to be stored in batteries until needed (blackout)

Concept:
A fish tank is just a box of potential energy, this energy is released as the water falls down the standpipes in the overflow to the sump/fuge or whatever. Mini scale hydro electric damn.

Initial reading:

My thermodynamic's textbook

DIY website http://www.builditsolar.com/Projects/Hydro/hydro.htm

And http://homepower.com/basics/hydro/

Ive got alot more reading to do before I have any loose numbers, but I thought i would get the topic going. Maybe someone else has done/thought about this.