The following is a list of aquarium diseases. New fish can sometimes introduce diseases to aquaria, and these can be difficult to diagnose and treat. Most fish diseases are also aggravated when the fish is stressed. Common aquarium diseases include the following: * Amylodinium (marine velvet) * Anchor worms * Columnaris * Cryptocaryon (marine ick) * Dropsy * Fin rot * Skin or Gill Flukes * Ichthyophthirius (white spot or ick) * Velvet Disease, including Oodinium * Hexamita (hole in the head) * Lymphocystis * Flexibacter columnaris