Pond Boss Forums GENERAL QUESTIONS Water chemistry Sulfur content in well water to fill lake

I recently built a 10 acre lake and pumped it full of water from a nearby creek. I also had a well drilled to keep the lake full during the dry summer months. The water has a very high sulfur content and smells like rotten eggs. Will this water be bad for my fish or cause other problems later on if I use it to keep my lake topped off?

I'm no expert, but I know a a little about sulphur-smelling water. It's usually caused by hydrogen sulphide. H2S is very volatile, and breaks down in water quickly. Even a few parts per million of H2S in water can make it reek to high heaven, but is quite harmless to drink. I suppose it could be a bit more harmful to "breathe" for fish than for people to drink. H2S is acidic, so if you have to add well water often, your pond water's Ph may go down just a tad, depending on the concentration in your well water. Bottom line, probably no worry at all, but slight problems not to be ruled out entirely.

Water in our area very commonly smells that way...before the advent of filters and submersible pumps on 4 inch wells, it was a common process to pump the well water into a holding tank which was open to the air, but not insects. The exposure to air removed the smell and presumably the sulpher that causes it...not sure why, not a chemist, but it worked and says to me you have nothing to worry about.

I think that when exposed to air, the Hydrogen Disulfide ("rotten egg gas") dissolved in the water just outgases (osmoting (sic?) to a region of lesser concentration, the air).

I believe H2S is one of the products of anaerobic decay in the bottoms of ponds without sufficient oxygen there. While present in the lower water, it isn't noticeable at the surface unless there is a sudden turnover (again, it's leaving the upper water with contact to the air, I assume).

When we were looking for farms 20 years ago, sulfur in the drinking water well was the one thing that killed our interest in one nice place. And I still remember drinking Grape Koolaid made with sulfurous water in New Mexico on vacation in 1968!