The water bucket that my brothers dogs use in the kennels gets green and slimy. It makes me SOOOO angry!! If I ever leave Zoee there I will stop and clean out the water dish completely. I can't believe they let their dogs drink out of it. OH, and the water bowl at their house gets icky too. All they do is refill it. When I'm there I clean it out then fill it.
I don't say anything because I don't want to anger my big brother. He is, afterall, always watching Zoee for us. So I just quietly (well, most of the time I'm quiet about it ) take care of it myself.

I had read a story before, I'm sure it was here on PT, about a dog that went swimming in a lake or something then died a few hours later. And it was due to the algae in the water. The dog wasn't even "drinking" the water. It was just the small amount that the dog accidentally ingested while swimming. Probably swimming out and fetching toys.