I have pond in Allegany County New York (about 1 hour south of Buffalo). The pond is spring feed and has rainbow trout. The size is 1/2 acre and is 15 feet deep. The trouthave a musty, mildew type odor. They also have the same taste. Anyone have any thoughts? If I changed the pond over to perch or bass wouldthe same thing happen?

We have the same issue up here with rainbows from larger lakes and small ponds alike. It seems to go away in winter. I don't care for the taste and usually don't eat them. I've read it is caused by a compound called geosmin, produced by certain types of algae. Some ponds are worse than others. Trout growers will place them in fresh flowing water to purge them of the off-flavour before sending to market. I have had yellow perch from the same lakes as the yukky rainbows came from and found no musty, earthy taste. I know some people that smoke the trout and they taste fine.

Geosmin and other "off flavor" producers in fish are caused by chemicals produced by certain species of algae when it is "blooming". These chemicals are absorbed by fish and then released back into the water when the algae bloom subsides or if the fish is transferred into water without the blooming algae. The off flavors occur most often during warm weather when the problem algae species blooms best.

Cody nailed it. The taste and smell has less to do with what the fish eat than where they live. Summertime water has life beyond fish. Plankton, algae, bugs swarm many lakes and ponds. Valuable as food chain, value drops when it affects the flavor of your fish.