The carp tastes better before the water warms up. When the water gets warm there is some growth of certain algae which produce an oily substance that causes the muddy taste. The carp also has less fat that could contain the flavor.
The fishy odor or taste is a sign of decay. When you stunt the growth of the bacteria the decay will slow down. I would not want to eat a fish that has been bleached to mask signs of decay.