Do fish have butt holes

The correct name for this is an anus. Fish eat food and everything it does not digest passes through the digestive system and out through the anus. Some fish like parrot fish eat a lot of coral. They chew off chunks of coral and 'poo' out the calcium carbonate of the coral as a fine sand. The reason that tropical beaches have beautiful white sand is because fish like parrot fish have chewed up the coral and passed it out of the anus.