Hyposalinity Treatment for Ich


Reefing newb
Here is a copy/paste of the hyposalinity treatment process from a well respected aquarist. I have used this process countless times with great results. Just be patient and follow to the T.

The hyposalinity treatment only treats a very limited number of ciliated parasites. The most notable in this group is Marine Ich (Cryptocaryon irritans). The home aquarist will not be using hyposalinity to treat any other disease or condition. Is this clear? I'll write it again -- hyposalinity cures ONLY Marine Ich.

A hyposalinity treatment will kill: Pods, snails, crabs, invertebrates, corals, live rock, most marine algae, and Marine Ich. This is why it is best performed in a separate, bare bottom, hospital tank. It has been performed successfully in fish only aquariums where there is no live rock and the substrate doesn't have worms and pods in it. But the best treatment tank is a bare bottom hospital tank, set up like a quarantine tank.

A hyposalinity treatment will not kill other parasites or conditions. A hyposalinity treatment does not kill Marine Velvet (Amyloodinium ocellatum), bacterial infections, injuries, intestinal parasites, external parasites, and a few hundred other diseases. Let's get to it!


Use a suitably clean tank or a setup/establish quarantine tank. The size should 'fit' the fish to be treated. About 5 gallons per inch of fish works out okay for this treatment, except for large adult Angelfishes, Tangs, and Rabbitfishes. For them, it would be better to use the ratio of 9 gallons per inch.

Lighting on the treatment tank should be dimmed so that you can see the fish, but not bright. Provide the fish with some hiding place(s) (e.g. PVC pipe, fake rock, etc.). Do not put substrate, live sand, live rock or any other kind of living thing in the treatment tank. A simple bare tank with a corner sponge filter is more than adequate. Use one corner filter for every 15 gallons of tank water.

Don't add/use power heads or strong circulating pumps. Set the tank up in a quiet area of the home, where there is minimal human traffic. Use heater or chiller and thermometer to hold temperature steady and constant. A UV may be used if you have one suitable for that size tank. Just don't overcook the water!
Do not attach a skimmer -- they don't usually work well with this kind of water. Besides, you should be making water changes to control organics/dissolved proteins.

DO NOT USE AN ELEVATED TEMPERATURE during treatment. DO NOT ADD ANY OTHER MEDICATIONS TO HYPOSALINE SALTWATER without knowing it is approved by the medicine manufacturer for use specifically during a hyposalinity treatment. When fish are in a hyposaline liquid, the effects of medicines and medications changes. Some meds become lethal, like copper. NEVER USE COPPER when doing the hyposalinity treatment.

The only different equipment needed besides the above is a refractometer. They are less than $50 and well worth the investment. A hydrometer is just not accurate enough for controlling the salt content in the treatment tank. Control will be essential to a successful treatment.

First Water and Water Changes
Water is taken from the display tank system or water is made up to match the water the fish is coming from. Match specific gravity, temperature and especially pH to very close to the water the fish is currently in, if water is being prepared from salt. The pH should be within 0.05 pH units -- that's how close I mean by 'close.'

pH Control
pH is hard to control in a hyposaline solution because at this dilution, the buffer ability of the diluted saltwater is not good. Be prepared for this.

Make pH adjustments with pure baking soda (e.g., Arm & Hammer) you find in the grocery store, or better yet is sodium carbonate. Sodium carbonate can be made in the home oven. Take a pound of pure baking soda and spread it out evenly on a large cookie sheet. Put into a preheated oven to 350F. Bake it for 30 minutes. Take the sheet out of the oven, let cool to warm and put into an air-tight, clean container for use. Now the baking soda has been turned into sodium carbonate, a more potent pH + additive.

DO NOT try to control the pH with pH buffer or other off the shelf additives. Use only the two mentioned above or a specific strong pH+ control.

Do not add the baking soda or sodium carbonate directly to the hospital/quarantine tank. Always thoroughly dissolve some powder in RO/DI or distilled water then drip/add that in slowly to move the pH up.

If you mess up and the pH has lowered considerably (more than 0.2 pH units) then raise the pH VERY SLOWLY -- no more than 0.10 pH units per day. A large pH change can seriously harm a fish, especially a sick one.


Lowering Salinity
Over a period of about 36-48 hours (use 48 for most Tangs, Butterflyfishes, Lionfishes, Puffers, and Dwarf Angelfishes) lower the specific through water removal and RO/DI or distilled water additions. Watch pH and temperature of the added water -- match that of the water being replaced. Use only a refractometer to measure the specific gravity. Lower the specific gravity to a reading of 1.008 to 1.009 sp. gr. units. Hold it there throughout the treatment.

This is why I mentioned above this treatment is not easy on the aquarist.
If the treatment tank has an active biological filter, don't assume it's working. When salinity is lowered the bacteria sometimes enter into a state of suspension and hold off in their metabolism of ammonia and nitrites. Controlling water quality and especially pH will be the challenge. Check for ammonia, nitrites, and pH twice each day at the start, until readings are zero for ammonia and nitrites. Don't count on the pH to remain steady. It must be checked no less than twice a day and if needed, adjusted.

Make water changes to control organics, ammonia, nitrites, nitrates, etc. If all is steady, still make water changes of 35% or more every other day. After the first water use, the only water to use to make changes is made up water from salt. DO NOT USE DISPLAY TANK WATER to make water changes in a treatment tank, no matter what disease is being treated.

The fish must be offered and gotten to eat throughout the process. The best foods must be given.
I would also seriously recommend the fish foods be fortified/supplemented with immune boosters during this time of disease treatment.

Salinity Control
If the tank water salinity is allowed to go up, the Marine Ich parasite will not be killed or stressed into submission. If the tank water salinity goes below the target salinity, the fish are in danger. HOLD THE SPECIFIC GRAVITY very closely within 1.008 to 1.009 sp. gr. units.

Treatment Time
The fish is kept in hyposalinity 4 weeks after the last spot is seen. After the last spot disappears, the hyposalinity continues for another 4 weeks. If during that 4 weeks, if any spot is seen, the time/clock starts over. There must be a minimum of 4 solid weeks with no spot EVER seen PLUS another four week to verify the fish is cured.

Raising Salinity
Now raise the specific gravity slowly. The raising of the specific gravity is very stressful on fish and this part must be done slowly. It should take 6 to 7 days to return the water to its normal salinity. Raise the specific gravity by about 0.003 sp. gr. units or less, per day. Less is okay. No need to be ultra conservative and go beyond 8 days to do this. BUT in no way try to shorten the time to less than 6 days.

When the treatment time is over, there is no need to add back distilled water to compensate for water evaporated. Let that be part of the raising of the salinity. When you go to raise the salinity, add small quantities of high specific gravity mixed and aged salt water.

Continue to monitor all water parameters and chemistries.


After the salinity is returned to normal, hold the fish in the treatment tank for another 4 weeks to verify it is cured. Look for spots every day, very closely. Observe the fish behavior, breathing rate, flashing (scratching) and look for any other Marine Ich symptoms. At the end of this time, the fish is cured/free of Marine Ich IF no other symptoms are seen/observed.

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What if the ich is in the main tank? I can do hyposalinity outside the tank. but once I put the fish back in won't they just get ich again?
What if the ich is in the main tank? I can do hyposalinity outside the tank. but once I put the fish back in won't they just get ich again?

You will need to do the hyposalinity outside of your main tank. If you were to do it in the tank you'd kill your inverts and corals. You'll also need to keep the fish out of the main tank for at least 8 weeks to allow the ich to go through it's life cycle and die off. After that when you put the fish back in they'll be safe from ich. Every fish you add to your tank after will also need to be treated with hypo before being added to your tank. Otherwise you'll just end up with ich again.
Brian is correct. You always want to treat fish outside of the main tank. I prefer to let tanks sit fallow for 12 weeks just to ensure the ich is exterminated. This is just my personal preference though. Best of luck!
This is great. I'm still debating on whether to do this or just feed the fish through the ich. It seems all the fish are happy, but I'd really like all the ich to be gone for sure.
Well...this is only useful if you plan on leaving your dt fallow for a few months (you can go hypo on your dt, but not if you have corals and other inverts). You can treat your fish in qt w/ hypo, but as soon as you put them back, they'll get ich again unless you treat your dt. If they're eating, they might fight it off themselves, which will make them stronger in fighting it if they get another outbreak.
Well...this is only useful if you plan on leaving your dt fallow for a few months (you can go hypo on your dt, but not if you have corals and other inverts). You can treat your fish in qt w/ hypo, but as soon as you put them back, they'll get ich again unless you treat your dt. If they're eating, they might fight it off themselves, which will make them stronger in fighting it if they get another outbreak.

True. I guess it would be easier to just take out my live rock and few inverts I have. Could I leave the sand in? I guess I would also need a sponge filter of some kind also?
oh crud! I just did a 50% water change to make SP 1.013 in 15 minutes instead of slowly over 2 days. I read some other article that didn't give a time frame for salinity change.....what the heck was I thinking???????
So far it's been 8 hours since I did the water change. The 3 fish seem to be doing well. I lost another clown 2 days ago to ich :( . Now the last ocellaris still has visible ich and the two new additions are being treating as well just to be on the safe side(cardinal and dartfish).