# Prophylactic Salt Unwise?



## DJRansome (Oct 29, 2005)

From a paper published in Copeiaâ€¦

Fuller, Rebecca C., "A Test for a Trade-Off in Salinity Tolerance in Early Life-History Stages in Lucania goodei and L. parva", Copeia 2008, No. 1, 154-157.

The two fish listed here are North American fish, with L. goodei found in mostly freshwater, and L. parva found in mostly brackish water, and are closely related. What was done was to breed these fish, the former in water with various concentration of salt added to fresh water and the latter to increasingly fresh water to determine the viability of the eggs and fry.

As the water got increasingly saltier, the L. goodie egg and fry viability decreased, and the opposite was not true for the L. parva. L. parva viability of eggs and fry remained virtually the same no matter the decrease in salinity of the water.

Does this mean that the use of prophylactic doses of salt could decrease the number of eggs you get, and the number of fry that may be raised to maturity for fish normally found in fresh water?


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## PsYcHoTiC_MaDmAn (Dec 26, 2005)

DJRansome said:


> Does this mean that the use of prophylactic doses of salt could decrease the number of eggs you get, and the number of fry that may be raised to maturity for fish normally found in fresh water?


I read this as, despite the spawn sizes remaining the same, fewer of the eggs were fertile, and even fewer of the fry survived.

the fact is, this seems to be common sense to me, the only reason for using salt for fresh water fish is to rid them of parasites or protect from nitrite poisoning.

I don't add "salt" to any of my tanks, (I use Epsom and bicarb, but purely for buffering capabilities and to bump up the TDS) and would strongly advise others not to unless there is a specific need


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## Number6 (Mar 13, 2003)

What studies like this show again and again is that tolerances vary from species to species and one should NEVER paint all species with the same color as a single one... unfortunately, we don't always keep this in mind and all too often some interesting fact gets passed along to ALL fish when it might have only applied to one...

studies like this CAN be used to help make educated guesses, but not much more than that.


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## DJRansome (Oct 29, 2005)

I thought they were trying to show that brackish eggs/fry are not harmed by additional salt but freshwater are.

Are there other studies that show prophylactic salt IS beneficial?


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## Number6 (Mar 13, 2003)

DJRansome said:


> I thought they were trying to show that brackish eggs/fry are not harmed by additional salt but freshwater are.


I did not see that hypothesis when I read the article. The article seemed to be suggesting only a mechanism for evolution.



DJRansome said:


> Are there other studies that show prophylactic salt IS beneficial?


 Yes, but usually dealing with some specific reason for the prophylactic use e.g. nitrite poisoning


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## PsYcHoTiC_MaDmAn (Dec 26, 2005)

Number6 said:


> What studies like this show again and again is that tolerances vary from species to species and one should NEVER paint all species with the same color as a single one... unfortunately, we don't always keep this in mind and all too often some interesting fact gets passed along to ALL fish when it might have only applied to one...
> 
> studies like this CAN be used to help make educated guesses, but not much more than that.


yet almost everywhere people will say that aquariums salt is good for fish.

its something that really gets me, when people go on about the buffer for their water, and people will just post add x amount per gallon of this that and the other without even asking what the tap water parameters are.

I dont have a problem with recommending the use of salt for specific reasons (reducing nitrite toxicity, eliminating parasites) yet I'm strongly against the attitude of just chuck it in with every water change.

the fact is, these fish come from FRESH water environments, sure there may well be trace amounts of salt, but I somehow doubt they'd be measured in PPT, more likely in a few PPM.

and as for the claims about it reducing osmotic differences making it easier for the fish to osmoregulate , IMO thats a load of bull. these are fish that have evolved in these salt free environments, if they are unable to osmoregulate effectively then there is something wrong with the fish.


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## DJRansome (Oct 29, 2005)

From reading lots of books, articles and forums, I've concluded that salt is a good treatment for an illness like ich, but is not beneficial and might even be slightly harmful to healthy fish.

I'd love to be able to quote something factual that confirms one way or another, however, LOL! Like PsYcHoTiC_MaDmAn said, it makes sense!


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## PsYcHoTiC_MaDmAn (Dec 26, 2005)

DJRansome said:


> I'd love to be able to quote something factual that confirms one way or another,


the problem is that there are so many freshwater fish, and some are adapted to take mildly brackish water, and some just have some genetic heritage that means they are better able to cope with it.

but IMO, if its not their natural conditions in the wild, then dont shove it in when their in the tank


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