I have a 45 foot long 15 feet wide(at widest point) spring-fed pond. It has 8 goldfish in it. I've had wild ducks move in the last 2 summers & spend a week to a month in it with their 10 ducklings. The raccoons play in it regularly. It has an outflow pipe that keeps the water moving. This year, the drought has dropped it 3 inches below the overflow pipe so it's not moving. It smells OK,& doesn't look stagnant, but both my dogs were vomiting all last week after drinking from it & never had that problem before. I fenced off the areas where they could access it, and they've been fine since. The fish seem OK, but I'm afraid it might be contaminated or something. We got enough rain yesterday to bring the level back up to but not through the overflow. Is there something I can put in it to clean it up? Any suggestions?