Mastering Freshwater Aquarium Ecosystems
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Fish Health (Cont.)

Since spironucleus occurs in wild fish, and wild fish never show the HITH/HLLE symptom it cannot be the cause. Many samples have been taken from the holes in aquarium fish that have often come up negative for disease. Many fish that have tested positive for spironucleus have no HITH pits.

Carbon has been suggested as a possible cause of HITH/HLLE, but it cannot be the cause since it occurs also in fish that are in systems that have no carbon filtration.

Stray voltage cannot be the cause of HITH/HLLE because reversal of the condition can take place in the same system where it developed without changing out any equipment.

Nutritional deficiency has often been suggested as a possible cause of HITH/HLLE, but fish that do have excellent diets can also show the symptom. Nutrition should always be balanced for the fish you are keeping. Even fish that are carnivores get vitamins from fish they eat that many have vegetable matter as large source of their diet. Some fish that aquarist think of as being strictly as carnivores, like many Central American cichlids will eat vegetable matter like nori seaweed, and boiled spinach as part of their regular diet.

Osmotic and pH Shock

Osmotic and pH shock occur in fish when the water chemistry drastically changes in a short time span, typically due to a water change or move to another aquarium. Symptoms are usually expressed by fish becoming lethargic, laying on the bottom of the tank, and heavy respiration. Death can occur within 24 hours if the fish are not returned to the original water chemistry they have become accustomed to.

Water chemistry should be adjusted slowly over a week or two when a major change is desirable. pH shock is common when a hobbyist does not do regular scheduled water changes and then tries to make up for poor maintenance practice with one large water change. This typically causes a drastic change in pH due to the new water not containing the pH reducing nitrate.

Bringing fish home from the aquarium shop is also a common factor in osmotic and pH shock. Not all aquarium/pet shops pay attention to the water chemistry of their aquariums. If the fish you are buying are kept in poor or incorrect water conditions, and you add them to correct/good water conditions they can experience osmotic and pH shock. It is a good idea to test the water in the bag for pH, and hardness before adding them to your aquarium. Adjust your aquarium water chemistry to be within 100 ppm hardness and .5 pH to avoid osmotic and pH shock.

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