Internal infections are difficult to diagnose. Often the fish show few external signs other than a loss of appetite and general lethargy. They often have stringy faeces. The causes of these conditions include:
The recommended treatments for each cause are different and as it is difficult to determine the exact cause, it may be necessary to try consecutive multiple treatments to determine the one that is effective. In all cases, stress should be reduced as much as possible and the water quality improved. These two actions alone may be sufficient for the condition of the fish to improve. If there is no noticeable improvement after reducing stress and improving water quality, it may be necessary to move the fish to a separate tank for treatment.
For bacterial infections, antibiotics are the treatment of choice. If the fish is still feeding, it will be of benefit to add antibiotics to the food as this will deliver the treatment closer to the site of infection. As it is difficult to ensure appropriate dosage of the antibiotics in the food and you can't guarantee how much the fish will eat, it is better to also dose the antibiotics in the water. Antibiotics should not be added to the display tank as they can inhibit the nitrifying bacteria. Useful antibiotics include Kanacyn (kanamycn sulfate), Furacyn (nitrofurazone) and Maracyn-Two (minocycline). Note that with Maracyn-Two, the recommended dosage should be doubled.
For nematode infections, piperazine may be effective. Like antibiotics, oral administration is helpful, if the fish is feeding, but is hard to control. It can be effective if added to the water of the treatment tank. Piperazine is available as Pipzine.
For intestinal protozoan infections, metronidazole may be effective. If the fish is feeding, soaking the food may be helpful. Metronidazole can be added to the water of a treatment tank. Metronidazole is available as Hex-A-Mit and Metronidazole.
Last updated: May 8, 2004