Hi Rick,
Most of E. Texas has a large amount of dissolved iron in there water. So my pond and temporary house uses well water. I am getting it straight from the aquifer 250 feet below the surface. Like most have started it will have a bad smell. Mine is so bad with iron it will start affecting the hose facets after about 2 years. I had to learn a lot about dissolved Iron quickly. Fortunately for me the guy that dug my will has a lot of experience with iron.

For my house he added an iron blocker that is self generating and added a water softener. that killed about 90% of the iron but on some day I could still smell something. He put in an (what he called) aerator tank. Basically a tank that the house water goes through before entering the house. He claimed the iron has a bacteria that not harmful to humans but that is what makes the water smell. When the water mixes with the air in this tank it will release the smell. Whatever it worked.

I put the well water directly into my 2 acre pond to keep it topped off in the dry months and I have not had any problems with fish dying or anything else. Good luck with your pond.
Joe