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Unread 09/13/2000, 12:00 AM   #17
Terry B
10 & Over Club
 
Join Date: Jan 2000
Location: Gig Harbor, WA. U.S.A.
Posts: 220
Hi Fish Junction,
What exactly what the problems hyposalinity that you are talking about? Yes there been many posts in the last couple years about people using hyposalinity and success rate has been phenomenal. The reason you don't see in a lot of posts about fish that don't tolerate a salinity of 14 to 16 parts per thousand is because most bony reef fish do very well. The studies that have been done suggest that the salinity must be maintained at 16 parts per thousand or less for the treatment to the effective. Cryptocaryon irritans can excyst (hatch) when the salinity gets any higher. The most widely accepted time frame for treatment is three weeks with fish. I see nothing wrong with extending therapy for longer It takes a longer period time to rid the aquarium of this parasite if the salinity is left natural levels because it can still hatch.
There are several precautions and restrictions for using hyposalinity correctly. First, never use it in the presence of invertebrates, live rock or live sand. Most invertebrates are osmoconformers, so their internal salinity varies with that of the surrounding water. Generally invertebrates do not tolerate wide fluctuations in salinity so they should not be exposed to levels low enough to effectively treat Cryptocaryon irritans. The microflora and microfauna that live on and in live sand and live rock are also damaged by exposure to a salinity this low. Second, elasmobranches, such as shark and rayfish, have a different osmoregulatory strategy than bony reef fish so they cannot be treated with this method. Third, the salinity and pH must be checked daily. Allowing the salinity to rise even slightly during treatment could result in re-infection. The alkalinity and pH will tend to fall in diluted saltwater, so these parameters should be tested frequently and adjusted as needed. I prefer to use Seachem’s Reef Builder™ to maintain the alkalinity and pH. Fourth, negative reactions to this therapy are uncommon with bony reef fish, but watch for signals such as hyperactivity, aggressive behavior, faded colors or difficulty swimming. I have personally kept a wide assortment of reef fish at a specific gravity of 1.010 for a period of three months at a time without any apparent ill effects. However, each fish should be monitored closely every day. The salinity can be lowered to 16 ppt indefinitely (Cheung, 1979.), but I do not recommend it on a permanent basis. There may be some variance in the ability to adapt between species, size of the fish or other factors. Fifth, many hydrometers are inaccurate or calculated for temperatures lower than a reef aquarium should be kept. An inaccurate reading during therapy could easily lead to treatment being ineffective. Many aquarists have reported swing arm type hydrometers to be off by several points when tested against a refractometer or an accurate glass hydrometer. Small glass hydrometers are often inaccurate as well.
I am curious to known what you measured the specific gravity with and what the water temperature of the tank was. According to Doctors Colorni, Chueng, and Noga along with the the reports in the scientific journals 16 parts per thousand or less low enough. You are correct that we can expect problems if we take the external salinity below that which is found in the internal fluids of fish. This is usually 11 parts per thousand or approximately a specific gravity of 1.008 at 78 degrees Fahrenheit. I have not seen any evidence to support the contention that Cryptocaryon irritans can adapt to such low salinities. Quite to the contrary, they cannot hatch from the tomont stage. If you saw an acceleration of the life-cycle at reduced salinities then I must wonder if you confirmed the diagnoses will use of a microscope. Uronema thrives at low salinties, Crypt. In my opinion, does not.
I have never advocated combining hyposalinity with copper therapy. I believe the two are a dangerous combination. The reason you are seeing more free copper in the water may have more to do with low pH and alkalinity rather than salinity. The pH and alkalinity tend to fall in diluted seawater. For this reason, I recommend testing these levels on a daily basis and adding a booster as needed.
HTH,
Terry B

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