Salt, Rays, and Osmoregulation

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Miles

Miles

Stingray King
MFK Member
Jul 2, 2005
5,547
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Spokane, WA
I was wondering if we could discuss some thoughts I had on Rays when I was reading through some recent articles.. About the negative effects of salt in certain types of fish (south america)..

In the past, I remember reading a specific article about the osmosis process that Freshwater stingrays possess.. It was pretty interesting. I dont remember the specifics and I'm unsure what part salt plays in their intake of dissolved solids.

I also have seen alot of pictures in which Exporters and Importers use heavy doses of Salt in shared and isolated tanks. Many raykeepers use salt as a gentle additive and preventative.

I have also seen alot of 'Sudden Ray Death Syndrome' and mysterious deaths often blamed to other problems, such as swallowed fishhooks and parasites.

I wonder if Salt, which can apparantly have damaging long-term effects on kidneys and other internal organs, could be causing a problem with stingrays?

Does anyone have any factual information about the absolute benefits of Salt in freshwater south american potamytrigons?
 
I do not have any clear cut evidence but I think of it this way.

All potamotrygons come from freshwater. The Amazon in general is a low Ph river system that has a very low hardness and an inability to buffer. Many rivers and tributaries have extremely acidic soft water.

These animals are not used to a high mineral content in their water. While the presence of some minerals are esential in the osmoregulation process, high concentrations lead to other problems. Anything that the animal takes in and does not need, will need to be processed and excreted.

An excess of salts in the water causes the kidneys of the ray to work harder than normal or necessary to excrete the excess. This may be no big deal or it may have lasting effects. There are many human diseases that cause the kidneys to work harder than they should and they are generally considered very serious.

I believe that the use of salt as a medication in the short term is fine. However, routinely adding it is not necessary and may due harm. Most of the US has sufficiently hard water that already may have too high a salt/mineral concentration. Teh average hobbyist should probably be taking salts out, not adding them.

Colin
 
The theory as to why salt is helpful for rays is that the osmolality of their blood is much higher than fresh water, so there is a constant energy requirement necessary to maintain the ray's blood at the proper level. When a ray [or any fish] is stressed [shipping, disease, etc.] raising the osmolality of the water in the tank reduces the difference between the blood and the tank water, thus reducing the energy loss for stressed fish.
 
i have never used salt in my tank for ANY reason
 
I think it might have to do with the conductivity of your water.. My water here is really hard and high in nutrients, so I don't think there is a huge need for an added amount of dissolved solids.
 
Bump to continue this discussion...
 
stingrays1;1136219; said:
The theory as to why salt is helpful for rays is that the osmolality of their blood is much higher than fresh water, so there is a constant energy requirement necessary to maintain the ray's blood at the proper level. When a ray [or any fish] is stressed [shipping, disease, etc.] raising the osmolality of the water in the tank reduces the difference between the blood and the tank water, thus reducing the energy loss for stressed fish.
Click to expand...

so it holds no long term effects for the ray?? what about keeping salt in the water at all times?
 
If it reduces the energy lost then I dont see how it would hurt them. I do keep salt in with my rays BUT I also go for a month or two out of the year without salt.
 
I have just recently had a problem with my pearls not eating for almost two weeks, Now I have one central system so my water is the same in all my tanks. I normaly do not keep much salt in my system but decided to add a large amount as a last resort to see if it would help get the pearls eating. Within 24 hrs my pearls had there full appetites back and were alot more active. Prior to adding the salt I would feed a tank of 8 pearls 140 night crawlers once a day and they would always eat everything, by the time they had stopped eating they would only eat 20 worms a day and would not eat any shrimp or silversides. After the salt dose of 2.5 lbs per 100 gallons they were all doing very well. I now will dose the system at any sign of stress or loss of appetite. I do not keep it in there all the time but do know alot of ray keepers who do and there rays all are thriving and breeding. I am pro salt and until i see any negative effects from it will always use it.
 
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