You have a choice to put different fish in the tank where they can be raised before being sold. Choose better fish to put in the fish tank. There are some fish that become as worthless by doing this. It is worth keeping even the smaller fish that are caught. Because your rod's and reel's durability decreases when used, every fish you catch and not keep is a waste of resources. Only get rid of fish if you are going for big ones or specific types.