Cleaning automatic waterers

The automatic waterer we're going to install next week is one of the aluminum ones from Nelson, but the one I already have is a Mirafount L'il Spring, which is plastic. We have hard water, straight from the well, and I am having a terrible time trying to keep the plastic one clean. I guess my next step is going to be to shut off the water to it, empty it out and fill the basin with vinegar and let it sit for a day, providing buckets for the critters in the meantime. I live in Iowa, so have to have heated waterers in winter.

Does anyone know of anything safe and effective that works on slime over crusty mineral build-up? Any tools that work particularly well to scrape on the contoured surface? Anything safe that you can add to the "reserve" area that is also heated to keep algae from growing there over the winter?

Thanks!

--Kristi