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Osmotic Stress, Osmotic Shock

Symptoms: Abnormally light or dark coloration, unusual behavior (lethargy, hyperactivity), clamped fins, increased respiratory rate, possible loss of balance.

Treatment: Correct the pH level in your tank.  Using the appropriate pH buffer (sodium bicarbonate) to raise the pH is suggested.  Acids not containing phosphorous may be used to reduce the pH, but partial water changes to bring your tank to neutral are recommended.  Correct the levels slowly, using partial water changes.  The rate of change must not exceed 0.3 pH units per day.  Acute acidosis/alkalosis is commonly fatal, but a return to the normal level for the puffer is the only remedy.

Background: Osmotic Stress can be caused by improper water parameters with extreme amounts of minerals (rich or depleted).  Some species of pufferfish have less efficient osmoregulatory systems, and can't adapt to such extreme conditions as easily.  Extremely soft or hard water is often the culprit, depending on the species.  For pufferfish it is often the former.

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