Remove the skin of the carp. Take out all the brownish-redish-colored part of the meat, the "mud vein"; discard. Chunk up the rest of the carp fillets. Place fillet pieces in a shallow dish. Pour the buttermilk over them and let it stand for half an hour, turning the fillets over once during that time. Stir the salt into the biscuit mix.
Take fillets out of the buttermilk and pat them into the biscuit mix, covering both sides. Fry fillets in deep fryer or in hot oil in fry-pan for 5 - 10 minutes until cooked through and browned on both sides. Use tongs or slotted spoon to turn them. (If oil is too hot, they will brown too quickly and not cook within.) Drain on paper towels. Serve with lemon wedges if available. Serves 4-6.