Hyposalinity (Osmotic Shock Therapy)

What It Treats Marine Ich (Cryptocaryon irritans) and Flukes (Monogeneans).

How To TreatPlace the fish you wish to treat in a quarantine tank with SG & temperature matching the tank they came from. Over a period of 48 hours, gradually lower the SG down to 1.009. You must use a perfectly calibrated refractometer at all times while doing hypo. Treat for 30 consecutive days, and during that time the SG must always remain at 1.009. If it inches up even slightly, the 30 day clock restarts. For this reason, many people use an auto top off system while performing hyposalinity. Some have even used hypo to successfully rid their display tank of ich, while others have failed. All corals and inverts must be removed beforehand if you wish to try this.

One of the challenges posed by hypo is maintaining a proper pH for the entire duration. While fish aren’t overly sensitive to low pH for short periods of time, anything continuously lower than 7.5 is going to be a problem. So, you will have to constantly test and then buffer the water to raise the pH. This can be accomplished by using supplements (available at most LFS) or you can “bake” your own DIY supplement by using baking soda. Spread baking soda onto a clean baking sheet, and bake at 300F for 1 hour. This process drives off carbon dioxide and water from the baking soda, and the result is an effective pH buffer. You will need to experiment (start with a very small amount) to determine how much is needed to raise your pH to the desired level.

ProsChemical free solution to Marine Ich, and is gentle on most fish. Scientific research also showed hyposalinity at 15 ppt (1.011 SG) for 2 days eliminated juvenile and adult flukes. When maintained for 5 days, egg hatching was prevented.

Cons/Side EffectsDifficult to execute properly, and hypo resistant strains of ich have been proven to exist (study done by Yambot in 2003.) In addition, hypo oftentimes will suppress (but not fully eradicate) other parasites such as velvet, brook and uronema. This does not become evident until salinity is raised. So, it is very important to be sure your fish has Marine Ich, and not some other parasitic infestation, before beginning hypo treatment.