I’ve caught plenty of catfish that if not properly fixed, would have that muddy taste. The best thing to do is to soak your fillets in buttermilk overnight. I’ve read it helps pull the oils out of the fillet that gives them that muddy taste. I’ve done this many times and they have always turned out well.
CGato
Put them in a big live well with clean water and feed them cornmeal for a week, that’ll flush the nasty out of them.