Hi, all –

I’ve read that adding some freshwater aquarium salt to my tank (26 gallons) can have several benefits. However, I’ve also heard that the salt can damage plants and corydoras. Likewise, though, I’ve also heard that in lower concentrations, corys and plants can still do okay.

What’s your personal verdict? Can you provide a link or go into detail about personal experience on this? Thanks in advance!

What benefits are you specifically looking for in adding salt to your aquarium? 80-I00 years ago salt was recommended for all sorts of maladies, in part because the hobby had so little else to treat diseases. Today we know that dirty water (more nitrogen compounds especially) can inhibit the fish’s ability to absorb enough oxygen. That in turn compromises their immune systems and trouble can follow. 80-100 years ago "they" would have been astounded by the idea of treating tap water with an appropriate water conditioner. Of course they didn’t have all of the stuff put in the water we do today. They would have understood letting the water sit a couple of days to absorb oxygen and maybe shed noxious gasses. But they would be amazed at the increasingly common suggestion that one strive to do a 50% or even a 70% weekly partial water change! (In most head-water streams and forest ponds where many of our aquarium fish come from nature changes 90+% water daily)

Either coming in on the fish or as chlorine-resistant cysts through the water mains, we often have a non-lethal population of velvet, Ich, fish TB (Mycobacterium marinum) among others. If we didn’t put new purchases in a covered jar, gradually add tank water over an hour and then pitch all of the shop water in the bag (rich as it may be in urine, feces, shed stress hormones, pathogens, possibly residual medications from the shop….) then we really seed our tanks with stuff we don’t want.

Aquarists that buy fish to breed in single species tanks often accidentally quarantine new purchases. We should all do that to protect our friends in the regular aquarium, but who has the time, extra tank and space in the house?

When we treat for Ich, salt is often used. It irritates the skin which produces more mucus, entrapping some of the Ich organisms under the mucus. However some of those may survive to seed are tank later and cause an outbreak when tank care falters.

There is also the drawback that if epidermal cells in the skin are producing mucus, so are the gills. And at a point, that can be harmful.

You didn’t mention what kind(s) of fish you wish to work with. 1000s can qualify as aquarium fish. Some can not stand a gradual temperature increase to the high 80s F. If they can and Ich breaks out, try a 50% water change (or several) and gradually raising the temperature before anything else. Ich can’t resist 88 F.

It is not recommended, but if you are using water from your home’s water "softener", you are already putting sodium chloride in there. Those devices are necessary with mineral rich waters or we would have trouble getting rid of the soap washing clothing or bathing. However for every molecule of the hardness substances like calcium or magnesium the basement water softeners take out, they add two molecules of salt! Generally it is recommended that we draw from the cold water tap and let the water warm up.

Municipal sources in our community work with very high levels of mineral already in the water and run it all through a community-sized basement water softener. We have 160 to 225 PPM (sodium) already in the water. One can do a little desertification project watering house plants. New residents moving here with high blood pressure have a higher blood pressure problem after a few months. (Fortunately those w/o blood pressure issues usually aren’t harmed by drinking the water, at least in terms of blood pressure.).

If you aren’t interested in breeding fish, a little salt in the water isn’t so important.

Even though I add 8 or 9 parts RO (demineralized) water for every 1 part tap water, I’m having trouble getting some rainforest fishes to spawn and it is a struggle to keep the broad-leaved water sprite (perhaps the all-time best best fry shelter) alive. I probably will have to completely remake the RO water using a modest measure of cichlid salts or a product like Equilibrium or switch to all livebearers, Central American cichlids or brackish water fishes.

If you have a good water supply, you are able to properly prepare it for your fish and you can keep up (most of the time) with significant weekly water changes, go the prevention route rather than using salt.

Having been away, I have had disease outbreaks in tanks left without weekly water changes. In one aquarium where rainbowfish were dying one a day, most were saved by doing a 30% water change the first day and doing water changes almost every day at 40%, 50%, 50%. A week+ later they were laying viable eggs again, always an indicator of fish health. If we had taken the time and expense to get a pathologist (ka-Ching!) to analyze what the disease was, all of the rainbows would have died in the meantime.

If you wish to mention the fish you are interested in by editing your question, perhaps a little more could be said.

Good luck & all the best!