Discussed below are some of the common saltwater fish diseases. Of these diseases some are infectious and if proper treatment is not provided these diseases can lead to death of the fish.

• Bacterial Diseases: Bacterial diseases are caused due to pathogenic bacteria and are very common among fish. Bacteria can attack externally or internally and can damage organs leading to death. Of the bacterial diseases skin rot and gill diseases are the most common.
   
• Fish Lice: Fish lice (argulus) are amongst the largest found parasite in animals which is about a centimeter long. They clamp themselves to the body of the fish and suck out the fluids. They are clearly visible through the naked eye but still you have to check for it especially in the hidden areas behind the fins. When these parasites attach themselves to the fish the fish feels uncomfortable and moves its body a lot.
  
  
• Flukes: These are also parasites, though harmless when few in numbers but can be fatal if found abundantly on fish. Flukes use their hooks to clamp to the body of fish and are not visible through naked eye because it is around 2 mm in length. Once struck to a fish fluke completes its life cycle and is considered the most difficult to treat. When treated with malachite and formalin the results have been positive.
  
  
• Ich: This is also a parasite commonly known as ich, ichthyobodo or costia. Though these parasites are harmless in nature and will not affect the fish but if the fish suffer from some other disease, ich begins to multiply at a very fast rate and start harming the fish. Due to the effect of this parasite the fish isolates itself from the rest and at some stage this would result in the death of fish.