I recently did an article about using hyposalinity to cure marine ich and how strains were found to survive salinity levels low enough to kill fish. You can read about the topic here: https://www.reef2reef.com/threads/hyposalinity-for-treating-cryptocaryon-irritans-marine-ich.313163/
Recommended Salinity Level, Process and Effects on Tank
So reading about hypo I noticed that its beneficial for the fish. This method is not intended for extreme hypo where it can start causing stress. For short term around 20 ppt (1.015) salinity can be beneficial, that can be used during quarantine. For DT with FO or FOWLR, I recommend 25 ppt (around 1.019), for reef tanks you can go to the lowest the inverts can tolerate 28 ppt (1.021) instead of the typical 35 ppt, you can argue its not hypo, but its less than the natural sea salinity. Its not recommended going too low with salinity level as in the long run it will have some issues on fish, especially urinal infections and possible kidney failure (in low saline environments, fish won't drink as much water because salt is not high enough in water taken in, this will cause toxins to develop in kidneys) and it can start stressing the fish in the long run defeating the purpose of it.
So if you decide to run hypo be sure to change salinity slowly, 0.002 change in SG recommended per day, although fish can tolerate dropping salinity better than raising it, so you can go up to 0.003-4 per day. If doing it in reef tank do it at slower rate and watch inverts for sign of distress. The equipment in the tank should be fine with this change in salinity, but the skimmer might need adjusting, as a change in salinity level will effect the surface tension and the creation of bubbles.
As you lower the salinity down there might be die offs, it will probably be either bacteria in LR or some types of algae (might also be inverts if it’s a FOWLR). Be sure to monitor for ammonia spikes. Biological filter should not be effected, but a mini cycle might occur from the die offs. Also make sure to monitor pH, lowering salinity might drop the pH slightly and correction might be needed.
If you want to raise salinity you can let the water evaporate, or you can top off the evaporated water with SW, make sure you don’t exceed 0.002 change in SG (2.5 ppt) per day as fish are more sensitive to increasing salinity rather than dropping it.
Benefits of Hyposalinity on Fish
Oxygen Rich Water
One of the main benefits of running hypo is rich oxygen water as lower salinity will allow more oxygen to dissolve in water. This is beneficial for fish as you want as much oxygen to be dissolved as possible, especially if a gill infesting parasite infects the fish, this will buy you some time until hospital tank is ready. When the fish is being medicated the medication will consume the oxygen in the tank, the lower salinity will allow for more oxygen to be available in water and might help with this issue, although its always recommended to provide plenty of aeration or surface circulation to allow for better gas exchange. Be careful when using medication with hyposalinity, although the levels here are not that low, but medications might be effected, prazi and antibiotics are safe to dose at these levels, I’m not sure about other medications so consult with the manufacturer or do the research (seachem claims that cupramine work in hypo environment, but less dosage is needed, 0.5 for SW and 0.25 for FW, so probably 0.35-0.4 for hypo will work fine, again consult them before performing treatment). Moreover, increased oxygen in water will reduce stress and thus provide better slime coat and immunity.
Hemostasis and Osmoregulatory Dysfunction Recovery
Another benefit of hyposalinity is to prevent dehydration in fish. Believe it or not due to transportation and other stress factors, the fish might have difficulty regulating homeostasis and develop osmoregulatory dysfunction, which can cause the fish to lose 10% of its weight in few days. Hyposalinity will help the fish absorb the lost water back for faster recovery from stress and return to normal homeostasis.
Reduced Metabolism and Appetite Recovery
In hyposalinity environment, the fish will require less energy in general due to rich oxygen environment, and also less osmoregulation, and other factors mentioned earlier, this will reduce the energy used for metabolism. In addition to that, most fish that stop eating is for a reason, the energy reserved for digestion is being used for other higher priority options like recovering from injury, metabolism, etc. which the body deemed necessary for survival. Since hyposalinity helped with those issues and is conserving energy, the energy will be used back for digestion, thus the fish will start eating again (similar to when you get sick and you lose your appetite).
Healing and Growth
In case the fish is wounded, hyposalinity will help it decrease fluid loss by lowering the osmotic difference between two liquids. This is usually done by the slime coat on the skin. Furthermore; since hypo reduce the energy consumption for metabolism, breathing etc., this energy goes into repairing the damaged area or healing up the wound and thus faster recovery. Once the wound is healed, the energy will be used in growth and development of immune system, providing better overall health of fish.
Finally, hyposalinity seems to rebalance the energy used by the fish and focusing on health and development rather than the other energy consuming processes. After all there is limited amount of energy a fish can take per day through food, and hypo will reduce the energy needed for metabolism, breathing, osmoregulation, etc. and rather invest the conserved energy in growth and protection. This method is highly recommended during quarantine as the fish is still stressed from transport and will help speed its recovery. Most online vendors and some fish stores keep salinity at around 25 ppt, so if you are quarantining you can drip acclimate it for few hours to 20 ppt and it should be ready to go through the quarantine.
I tried TTM at 35 ppt three times but didn't succeed, I lost a fish and the other two were stressed and stopped eating, which made me stop TTM and remove them, I tried 25 ppt and it worked every time since, Prazi no longer seem to make the fish stop eating, although I can still notice a slight loss of appetite and decreased eating after doing prazi, but after looking up this topic I'll start doing 20 ppt hopefully this will make it a stress free environment for the fish. I hope you enjoyed the topic and found it beneficial.
And as always Happy and Safe Reefing
Recommended Salinity Level, Process and Effects on Tank
So reading about hypo I noticed that its beneficial for the fish. This method is not intended for extreme hypo where it can start causing stress. For short term around 20 ppt (1.015) salinity can be beneficial, that can be used during quarantine. For DT with FO or FOWLR, I recommend 25 ppt (around 1.019), for reef tanks you can go to the lowest the inverts can tolerate 28 ppt (1.021) instead of the typical 35 ppt, you can argue its not hypo, but its less than the natural sea salinity. Its not recommended going too low with salinity level as in the long run it will have some issues on fish, especially urinal infections and possible kidney failure (in low saline environments, fish won't drink as much water because salt is not high enough in water taken in, this will cause toxins to develop in kidneys) and it can start stressing the fish in the long run defeating the purpose of it.
So if you decide to run hypo be sure to change salinity slowly, 0.002 change in SG recommended per day, although fish can tolerate dropping salinity better than raising it, so you can go up to 0.003-4 per day. If doing it in reef tank do it at slower rate and watch inverts for sign of distress. The equipment in the tank should be fine with this change in salinity, but the skimmer might need adjusting, as a change in salinity level will effect the surface tension and the creation of bubbles.
As you lower the salinity down there might be die offs, it will probably be either bacteria in LR or some types of algae (might also be inverts if it’s a FOWLR). Be sure to monitor for ammonia spikes. Biological filter should not be effected, but a mini cycle might occur from the die offs. Also make sure to monitor pH, lowering salinity might drop the pH slightly and correction might be needed.
If you want to raise salinity you can let the water evaporate, or you can top off the evaporated water with SW, make sure you don’t exceed 0.002 change in SG (2.5 ppt) per day as fish are more sensitive to increasing salinity rather than dropping it.
Benefits of Hyposalinity on Fish
Oxygen Rich Water
One of the main benefits of running hypo is rich oxygen water as lower salinity will allow more oxygen to dissolve in water. This is beneficial for fish as you want as much oxygen to be dissolved as possible, especially if a gill infesting parasite infects the fish, this will buy you some time until hospital tank is ready. When the fish is being medicated the medication will consume the oxygen in the tank, the lower salinity will allow for more oxygen to be available in water and might help with this issue, although its always recommended to provide plenty of aeration or surface circulation to allow for better gas exchange. Be careful when using medication with hyposalinity, although the levels here are not that low, but medications might be effected, prazi and antibiotics are safe to dose at these levels, I’m not sure about other medications so consult with the manufacturer or do the research (seachem claims that cupramine work in hypo environment, but less dosage is needed, 0.5 for SW and 0.25 for FW, so probably 0.35-0.4 for hypo will work fine, again consult them before performing treatment). Moreover, increased oxygen in water will reduce stress and thus provide better slime coat and immunity.
Hemostasis and Osmoregulatory Dysfunction Recovery
Another benefit of hyposalinity is to prevent dehydration in fish. Believe it or not due to transportation and other stress factors, the fish might have difficulty regulating homeostasis and develop osmoregulatory dysfunction, which can cause the fish to lose 10% of its weight in few days. Hyposalinity will help the fish absorb the lost water back for faster recovery from stress and return to normal homeostasis.
Reduced Metabolism and Appetite Recovery
In hyposalinity environment, the fish will require less energy in general due to rich oxygen environment, and also less osmoregulation, and other factors mentioned earlier, this will reduce the energy used for metabolism. In addition to that, most fish that stop eating is for a reason, the energy reserved for digestion is being used for other higher priority options like recovering from injury, metabolism, etc. which the body deemed necessary for survival. Since hyposalinity helped with those issues and is conserving energy, the energy will be used back for digestion, thus the fish will start eating again (similar to when you get sick and you lose your appetite).
Healing and Growth
In case the fish is wounded, hyposalinity will help it decrease fluid loss by lowering the osmotic difference between two liquids. This is usually done by the slime coat on the skin. Furthermore; since hypo reduce the energy consumption for metabolism, breathing etc., this energy goes into repairing the damaged area or healing up the wound and thus faster recovery. Once the wound is healed, the energy will be used in growth and development of immune system, providing better overall health of fish.
Finally, hyposalinity seems to rebalance the energy used by the fish and focusing on health and development rather than the other energy consuming processes. After all there is limited amount of energy a fish can take per day through food, and hypo will reduce the energy needed for metabolism, breathing, osmoregulation, etc. and rather invest the conserved energy in growth and protection. This method is highly recommended during quarantine as the fish is still stressed from transport and will help speed its recovery. Most online vendors and some fish stores keep salinity at around 25 ppt, so if you are quarantining you can drip acclimate it for few hours to 20 ppt and it should be ready to go through the quarantine.
I tried TTM at 35 ppt three times but didn't succeed, I lost a fish and the other two were stressed and stopped eating, which made me stop TTM and remove them, I tried 25 ppt and it worked every time since, Prazi no longer seem to make the fish stop eating, although I can still notice a slight loss of appetite and decreased eating after doing prazi, but after looking up this topic I'll start doing 20 ppt hopefully this will make it a stress free environment for the fish. I hope you enjoyed the topic and found it beneficial.
And as always Happy and Safe Reefing
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. But yes hypo might kill other parasites that might slip in with the fish, but didn't mention it here as its not always guaranteed method.
