Question
Hi...I just bought a fountain for my patio.  It has a copper pipe that draws the water up from the pump and pours the water into the first basin, and so forth.  The water is clear when we start out, but after a day or two it turns green.  We've tried pond algaecide from Lowe's, and have changed the water twice.  Please, any advice would be helpful.  Thank you.

Answer
It does sound like you are experiencing an algae problem, although it is remotely possible that it is the copper piping.  The algae in question sounds most like planktonic algae.  There are literally millions of different species of planktonic algae, so finite identification and eradication is more of a process than a one-step cure.  On that note, the only one-step cure is to add chlorine bleach in a 1:10 ratio weekly.  This is only an option if you do not plan to have any fish and do not have a household pet that would drink out of it.

The other option you could try is to use distilled, deionized, or reverse osmosis water.  This will be free of the nutrients that algae demand for growth.  However, if any leaves, pollen, flower pedals, etc. fall in the water and decompose, those nutrients would then be available.  

Plants use these same nutrients, and often use them faster than algae will.  You could try a hydroponically grown aquatic plant and avoid needing to add soil, as soil is a very messy thing to put in a water fountain.  You would still need some sort of substrate, like clay chips or pea gravel, unless you got a floating plant.

I hope you can effectively employ one of these strategies to solve your algae problem.