Tropical Fish Keeping - Aquarium fish care and resources

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Jmoney 09-05-2007 08:51 PM

Freshwater Aquarium Salt?
Does aquarium salt for freshwater tanks actually help keep the fish healthier or is it just another way for companies like API and the fish stores to make money?

jim21 09-05-2007 09:51 PM

I do believe it is helpful for fish - especially sick fish. I have seen a noticable improvement in sick fish when I add a couple T of salt with the medication. It also helps with electrolytes. I've been using it in all my tanks every since the first one was established.

Hope that helps,

jones57742 09-05-2007 10:02 PM


This is a "raging topic" in the fish keeping world.

I am in Jim's camp.

I typically keep a salt concentration of (in US) 1Tblspn/20G or less.

I believe (and this is hotly debated) that these low concentrations are not toxic to fish but these concentrations reduce or eliminate viral and/or biological pathogens.


mHeinitz57 09-06-2007 07:40 AM

Most people don't even know what salt actually does for fish and I know it doesn't even say so on most product containers. You wiull often hear that salt improves gill function or adds electrolytes or reduces stress, etc...and that is all true to an extent. The main purpose of salt though is for Osmoregulation...

The cells in a fish's body have a certain salinity level inside them, just like our cells do. The water outside of the fish normally has less salt density than the cells. Because the cell walls are permeable, the fish continually "leaks" out salt into the water. In order to compensate, the fish consumes a large quantity of water to get that salt back. There are also sodium ion pumps in the cell walls that continually have to bring salt back in. All in all, the fish is always expending a certain ammount of energy to maintain a specific salt level in its body.

When you add salt to the tank, you raise the salinity of the water and therefore the fish does not "leak" as much salt. The fish can therefore conserve energy which can boost the immune system, reduce stress and improve respiratory function. I like to compare it to how us humans will lay in bed when we get sick. This allows our bodies to use all of its energy to fight off disease and is why salt is often suggested for treating disease in fish. In salt water tanks you do the opposite. Saltwater fish are constantly taking in salt because the salinity outside the fish is greater than inside the fish cells. The saltwater fish have to expend energy to expell excess salt so when saltwater fish get sick you often lower the salinity of the tank.

That being said, there are pros and cons to using salt. I personally only use it when I have a fish that seems ill or stressed. This is because while it is good for us to lay in bed when we are sick, no doctor will ever tell you to lay in bed 24 hours a day for the rest of your life! If you did that, you may be exposed to less diseases but your immune system, circulatory system and respiratory system would become weaker because it doesn't get a workout. I think using salt at all times can actually create weaker fish and I think the salt is more effective at treating disease when it is not used all the time.

fish_4_all 09-06-2007 11:39 AM

Well science aside, I used to use salt in all my tanks. It kiiled my plants and I had at least 3 ich outbreaks while using it. I also normally lost 1-2 fish every couple months while using it. I have since stopped for 2 reasons:
#1 is I have live plants and htey do not do well with much more than tap water concentration fo salt.
#2 is because my fish losses have greatly decreased in the past 1.5 years since I stopped adding salt. The only major loss I had was when I did not quarantine new fish and had an ich outbreak. I treated with Coppersafe only and the ich was gone in less than a week. Yah it took over a year before snails lived in the tank again but that is what I get for not having a quarantine tank at the time.

One word of advice if you do use salt is to get a hydrometer so you know exactly where the concentraiton is and aren't guessing so the fish are not stressed out by too much. Also, add the salt to the water before you put it in the tank. This will make sure that the concentraiton is the same and won't shock your fish and possbily kill them from a water change. Osmotic pressure can cause serious damage very fast if the concentration changes too rapidly. Many cfish can transistion from salt to fresh and back but simply dropping them in salt water from fresh water will quickly kill them. Brachish shouldn't be as harsh of a change but why take the chance?

jones57742 09-06-2007 05:58 PM


Just to make sure here:

1) the topic is sodium salt;
2) the topic is salt which can be purchased at an LFS or in an aquarium section in a pet store and
3) the topic is not table salt (table salt is toxic to fish even in low concentrations).


I got to tell you partner that your post is the absolute best treatise which I have ever read concerning this topic (and please believe me that I have done tons of research prior to and since reentering fish keeping).

I know that it's preparation took a tremendous expenditure of time and I really appreciate it.


mHeinitz57 09-06-2007 06:23 PM

Thanks TR, that means a lot coming from you. It actually didnt take long to write since I've given that speech to customers many times before, lol.

mHeinitz57 09-06-2007 06:27 PM

oh PS...for people with larger tanks that want to save money on aquarium salt.

It is the same salt as "solar" or water softener salt. THe fish stores i've worked at we would just run to Home Depot or Lowes and buy bags of it for cheap for the huge display tanks. It was the same exact stuff as if we had ordered large bags of aquarium salt from corporate HQ.

jones57742 09-06-2007 07:05 PM


I am not questioning your post but only making a few comments based on my research of the literature.

Salt marketed for water softeners contains a small percentage KCl and also contains other impurities (I cannot remember all of these now) which may be toxic to fish in the small quantities in which they are present.

The above paragraph is applicable to "ice cream making salt" as well as to de-icing salt.

Having said that "who knows" but what the aquarium salt which we are discussing may not contain concentrations of KCl and the stated toxic impurities.

Have you ever??? had a problem with the use of water softener salt and if so what was (were) the problem(s).


mHeinitz57 09-06-2007 07:14 PM

Personally I have never had any problems with the use of these salts and I know that large pet stores use the same stuff on a regular basis to help with the raised stress level that a store produces. Yes the safest bet is to use products marketed as "aquarium salt" but personally I don't see any downsides to using some alternatives. As I mentioned earlier though, I rarely use salts in my tank except for treatments but I have treated an oscar with ich by using softener salts and it was successful.

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