So ... Salt Or No Salt?

[Zekumi]

I'm confused.
In the Livebearer's section, I've of coarse seen and/or read the 'Mollies Need Salt!' pinned topic. I've got Mollies, so I bought some salt right there in the beginning and've been using it ever since.

Now I'm hearing (from multiple sources) that aquarium salt is useless in freshwater unless I'm treating for Ich or a parasite and so forth ...? My tank's a community tank. Should I discontinue adding the salt? I love my Mollies, and I want them to be healthy, but I think I'm getting mixed messages here.

 

[OldMan47]

If you decide to go with salt for your mollies, you want to use sea salt, not "aquarium salt". If you have the mollies in a tank with fish that do not tolerate salt well, you need to know that all mollies that you are likely to find in a fish shop will tolerate any amount of salt from none at all to full sea salt. I worry more about what is called TDS, total dissolved solids, with my mollies. Mollies do not do well in low solids content water. They also do not do well in low pH water. Sea salt will raise pH and will raise TDS so it does work when you start with very soft water. I have relatively hard water from the tap and never use salt with my mollies. My TDS measures between 250 and 325 ppm depending on the time of year. In terms of hardness that translates to between 12 and 15 degrees of general hardness, GH. The KH of my water runs in the 10 to 12 degree range which means that my rather high pH is quite stable.
The real message should be that mollies do not do well in low pH and low solids water, one way to raise both is to use sea salt if the other tank occupants can tolerate it. I find the arguments that happen over salt and no salt for mollies amusing because salt is not the real issue. The real issue, in my experience, is dissolved solids. Mollies need a fair amount of solids in their water and can tolerate tons of solids in their water.

This girl has been in my salt free tank for over a year and her fry were just born a few weeks ago in salt free water. It is far from soft low pH water. This is a picture from day 24 after the fry were born.

 

[Zekumi]

Aw, wow. The fry are adorable. n__n

Thank you for the quick reply. I wasn't aware I was using the wrong kind of salt (or rather that I'd misunderstood the whole matter entirely).

That makes more sense, though. I'll be sure to discontinue that aquarium salt and save it for various treatments instead.

 

[LauraFrog]

Well hold on - what's the hardness (TDS) of your tank water? Mollies will still fail to thrive if you keep them in soft freshwater. Your options with keeping mollies are basically hard freshwater or hard slightly brackish water. Generally when there are no salt-intolerant fish in the water, the recommendation is to add it anyway, although as said by OldMan, the water hardness is more important than the salt.

Does soap lather easily in your water? That's a sign that it's soft. If you have soft water and you want mollies to thrive, you need to be using salt, but aquarium salt (pure sodium chloride) won't be as good for them as marine or sea salt (which contains sodium chloride and other salts, such as sodium carbonate, magnesium sulfate, magnesium carbonate, calcium carbonate, calcium chloride, sodium sulfate etc). So adding sea salt to your water raises both the salinity and the TDS/hardness, which is why it helps keep them healthy.

With true sailfin mollies, IMO you cannot keep them in freshwater even if it's hard. I have never been able to keep them alive in under 1.005 SG - they are at their best approaching marine salinities. The 'pet store' hybrids are fine in hard freshwater or slightly brackish water.

 

[loachman]

Does soap lather easily in your water? That's a sign that it's soft. If you have soft water and you want mollies to thrive, you need to be using salt, but aquarium salt (pure sodium chloride) won't be as good for them as marine or sea salt (which contains sodium chloride and other salts, such as sodium carbonate, magnesium sulfate, magnesium carbonate, calcium carbonate, calcium chloride, sodium sulfate etc). So adding sea salt to your water raises both the salinity and the TDS/hardness, which is why it helps keep them healthy.

You can also find out an estimate of your water's hardness by checking with your local water supplier. Most have the information available online with their water stats. It's probably not exactly what you're getting from the tap (it'll vary somewhat depending on the day/time from last rain/etc.), but it'll give you a good idea.