There is just an awesome amount of information in this thread, obc! Here's an odd question for you, though--how do fish react to copper?
We have well water that tastes great and tests out perfectly for everything else, but is very high in copper. We have to filter it before drinking it or cooking with it...that's how high the copper is (evidently the aquifer the well tapped into runs past the copper deposits near here). I'd love to try a tank, but if fish are intolerant of copper, everything would have to be filtered or transported in from some other water supply...