Hyposalinity therapy
Hyposalinity therapy has numerous advantages over copper-based medications (Bartelme, 2001c). This method does not suppress immune functions such as phagocytic activity. Antibiotics can be used in conjunction with hyposalinity therapy. Some antibiotics are more effective, or a lower dose is required when the salinity is less than that of natural seawater. The salinity only needs to be checked once a day while administrating treatment. Chemical filters such as carbon and Poly Filterรขโยข can be used when employing hyposalinity therapy.
An accurate means for measuring the salinity is crucial when treating fish with hyposalinity. Swing-arm type hydrometers are notoriously inaccurate. A refractometer, or lab grade, large, glass hydrometer is recommended. Alkalinity and pH tend to fall in diluted saltwater. Check these parameters daily and add a buffer as necessary to maintain the pH between 8.1 and 8.3. Do not expose elasmobranches, invertebrates, live rock, or live sand to treatment with hyposalinity. This method is safe for the bacteria that perform biological filtration, at least if the salinity is not dropped too rapidly. Make two water changes per day for two days, reducing the salinity about 5ppt per water change.
Maintaining the salinity at 16ppt or less has proven to be a highly effective treatment for cryptocaryonosis (Bartelme, 2001a, b). However, this may change with if low salinity variants of Cryptocaryon irritans become common or widespread. The salinity (not to be confused with specific gravity) must be maintained consistently at 16ppt or less for the entire duration of treatment. I suggest 14ppt to allow for any fluctuations in the salinity during therapy while providing some margin for error.
Treatment should continue for a minimum of three weeks after a therapeutic salinity level has been reached.
Unlike most other forms of treatment for cryptocaryonosis, hyposalinity does not target the "free-swimming" or theront stage. Hyposalinity therapy works by interrupting the life cycle at the tomont stage. Tomonts are destroyed by hyposaline conditions, thus preventing re-infection.
Teleost reef fish appear to adapt well to hyposaline conditions. Hyposalinity was also reported as an effective treatment for cryptocaryonosis by Angelo Colorni of Israel Oceanographic and Limnological Research Ltd 1985 (Colorni, 1985). A report in Drum and Croaker stated: "We now have experience that proves that a wide variety of teleosts can live quite comfortably at รยฝ salinity (1.010) for extended periods of up to 2 to 3 months (Goodlett & Ichinotsubo, 1997). Emperor angelfish Pomacanthus imperator were the subjects of one such study. They were kept in salinities as low as 7 ppt for 30 days without any apparent ill effects (Woo & Chung, 1995).