Wow.

I went to a Petco with my mom yesterday to return a ten gallon she had bought that she didn't notice was cracked, and every single tank in the store a cup of salt in them. The catfish they had were flipping out, and very little was alive in any of the tanks. They had more snails than they had fish.

How long has Petco been doing this? I have not gone to one in a while and I certainly don't remember this.

lots of fish benifit froma little bit of salt, do you think every fresh water habitat has absolutly no salt in it at all?

i agree, but i think he meant that they were oversalting them and the fish were dying or becoming stressed

Scale-less fish will not benefit from salt (such as corydoras).

The presence or not of scales has no effect on a fish's tolerance for salt in the water. Catfish have no scales, yet Plotosus lineatus inhabits reefs. The Family Muridae has no scales, yet very few (if any) moray eels spend their entire life in fresh water.

What is more important is the ability of a fish to osmoregulate in water with salt in. Cories tend to have a low salt tolerance, but there is much variation between species (as Bignose has shown in a previous thread).

The short term use of salt in water can help with things such as nitrites and some parasites (and its use is a hang up from the days when water changes were considered bad). These short term lowish dose are unlikely to cause massive or long term harm. However, the "tonic" dosing of salt is far from likely to bring any real benefits (certainly none if you are also maintaining a good filter and performing water changes) and may be causing long term damage to any fish which have evolved in waters like those found in South America with extremely low salt levels.

That's simplifying it beyond any real meaning.

Though, to answer your question, there are many fish that develop in virtually salt-free conditions. Much of the Amazonian basin has salt levels that are only measured in parts per trillion.

The evolutionary history of the fish is among the bet clue as to whether a fish can tolerate salt or not. Freshwater fish are classified as either being a primary freshwater fish or a secondary freshwater fish. The primary freshwater fish have spend their entire evolutionary history in freshwater fish and hence never developed metabolic mechanism to deal with salt. Tetras and corydoras are good examples of primary fish. Secondary freshwater fish have spent some time in their evolutionary history in salt water conditions, and hence while the metabolic mechanism may not be perfect, they have some mechanisms to deal with salt. It is vestigial (like mankind's tail bone). Cichlids are a good example of secondary freshwater fish.

Now, certainly these are broad categories and there are exceptions to the general rules. Lemon tetras come from a branch of the Amazon that has moderate mineral contents and aren't as intolerant of salt as cardinals are, for example. Discus do come from a branch of the Amazon that is very mineral poor, and despite being a secondary saltwater fish a cichlid, they aren't very tolerant of salt at all compared to many other cichlids.

But, the big thing is that one amount of salt in every tank isn't right. Some species will be fine with it, others are going to be very intolerant. And, if all their tanks are linked together to a central filtration system (like a lot of stores are) it probably isn't a good idea to put a lot (any?) salt in at all. The freshwater species that can deal with salt are almost always good with low levels of salt, but the intolerant species almost never are good with salt.

And, to SJ2K, it isn't the scale/no-scale issue. Corydoras do have scales, they just aren't the same as the ones on a tiger barb or a tetra or a cichlid. Corydoras are intolerant of salt because of their evolutionary history, they have never spent any time in an environment with significant amounts of salt. The Amazonian basin is almost wholly very acidic and mineral-free.

This post has been edited by Bignose: May 17 2008, 07:07 PM

Ehh. Petco has been doing this for.. a good 6+ months, at least at our petco. I remember them doing that early winter maybe?

I may not agree with the huge things of salt they put in there at all, but at least they tried.
There were a few tanks without bowls of the stuff -- but still.. they put such a large amount in there, I know exactly what your talking about. lol.

Mines been doing it as long as I can remember. Its always way too much salt IMO. Like 1.5 cups of salt sitting in a cup at the bottom of the tank. It doesn't even seem to dissolve very well.

Would it harm them though (clown loach)

Clown loaches have been reported in brackish waters in the wild, so I doubt a small amount of salt in the water will do any long term damage

I wasn't saying that salt is completely bad, but that they are using way too much. It's honestly about a plastic drinking cup in every tank full of salt; Some even had two.

We're not talking '1tbsp per gallon' or whatever though, by the sound of it they're chucking in a load of undissolved salt which isn't a very good idea...

are you absolutely sure it was salt? could it have been coral sand if they were experiencing a pH crash and were trying to buffer the pH up to a more acceptable level?
or something else?

I had a petco in a near by city, however it has since closed. I went in there a couple of times, and do remember seeing cups of salt sitting inside all of their tanks. It was large "pellet" pieces of salt, similar to what you would put in a water softener.

I think it is a quick fix solution for them when they start to lose massive amounts of fish to disease, ext.

Kind of funny, some new to the hobby people have come into my store being told they have saltwater fish, (thats what the petco people said), when in reality it is actually tetras.