Robert,
We used to catch catfish out of the river and sometimes the bigger ones had a muddy taste to them. My Grandpa would throw them in a horse trough with clean well water in it. In a couple of days he would clean them and cook them- no muddy taste. He marinated bullheads and crappie in milk for a couple of hours- don't know if it was to get the muddy taste out.

Brad B.