I was raised old school when it came to freshwater fish tanks. One of the first things my mom reminded me to buy as I set up my first tank after moving out was to pick up a large package of aquarium salt. From there I listened to the package which will tell you that all freshwater fish do better with aquarium salt. It will also tell you that you should add one rounded tablespoon for every five gallons of water. This is a lot of salt, should you really add that to your tank?

Reasons to Add Aquarium Salt.

For years almost everyone added salt to their tanks and many local pet stores will still tell those that buy from them that they should be adding large amounts of salt to their freshwater tank. There are a number of reasons that people add salt and some of them are based on truth while others are based on myth.

  • Osmosis. A fish needs to have a perfect balance between the water in their bodies and the water out of their bodies. This is done through osmosis and salt can aid in that process.
  • Healthy gills. Salt can also help to maintain healthy gills in some fish.
  • Recovery from wounds. Salt is a great way to treat wounds (even on a person) and it can make a huge difference to some types of fish.
  • Keep away parasites. Salt in the water makes it harder for many parasites to live. So by adding salt you can get rid of parasites and you can also make it easier to keep them away.
  • Salt can also make it easier on the fish while the nitrites are high.

The basic idea was that by adding a decent amount of salt to your tank you would be doing all of the good things, all of the time. This seemed the best way to keep healthy fish for a long time. While it was an okay idea there are several things that we know now.

The Natural Habitat of Freshwater Fish.
Freshwater fish come from lakes and streams all over the world. Most of these places have very low amounts of salt and some have so little salt that it can't be found even when looking at millions of parts of water. Because of this many freshwater fish aren't really adapted to having salt in their water and it is best to avoid keeping salt in your tank at all times.

Times and Places To Use Aquarium Salt.

There is still a time and a place to use aquarium salt. However, you should learn what fish that you have that can handle the salt if you need to use it for longer periods of time.

  1. Starting a new tank. Because salt makes it possible for the fish that you have to handle the nitrite cycle of a new tank better it is a good idea to add salt to the new tank. You shouldn't keep it in there forever and you should slowly remove it as you change the water in the tank to make it completely fresh.
  2. Hospital tank. If you are into keeping fish and you want to keep your fish alive then it is best to have a hospital or quarantine tank available for fish that need it. When a fish has wounds or other problems you should put them in there. This can be a good time to add some salt. This is especially true if your fish has any signs or wear, tear, or wounds.
  3. Treating external parasites. Some parasites are treated well with salt and this is a much better option than many other chemicals designed for getting rid of these problems. It is best to research the particular problem that you have to find out if you should use salt, how much to use, and how long it should be in there. Some parasites will respond best if the fish is put into the hospital tank and the dose of salt is raised pretty high. They would then need to be left in there for about a half an hour and then the water should slowly be changed out so that the salinity is lowered back to normal in the next two hours. Others, such as Ick, need to be treated with salt for 21 days to get rid of it. Most fish won't have a problem living in the salt water for that period of time.

Fish That Like a Little Salt.

I think that there are three main reason that many local fish stores recommend adding salt to every tank at all times. First of all there are a lot of people who were raised old school out there. They were told that is what you do and they don't know why one would want to do that or the reasons that it really shouldn't be done, but that's what they do. Second, they have a vested interest in fish keepers adding all sorts of additives to their water. By adding all these extras they have more to buy and the more that a local fish store sells, well the better for them. Finally, many of the fish that the store sells do indeed do well in freshwater with a little salt.

The most common fish that are sold that like a bit of salt are the common live bearers including guppies, swordtails, platies, and mollies. These make up a large percentage of most local fish stores sales and these fish do best with some salt. In fact, platies and swordtails do really well in brackish water and can even be raised and bred in salt water! It is believed that these were saltwater fish that adapted to freshwater conditions and that makes it possible for them to move from one to the other (with gradual introduction).

Cichlids, particularly African cichlids often have salt added to the water. This is particularly good if they do some fighting and injure themselves. However, it should be noted that while many South American cichlids will also do well with a little salt, the Discus fish (a type of South American cichlid) isn't one of them.

Fish That Don't Tolerate Salt.

To the best of my knowledge, all fish can tolerate a moderate amount of salt for awhile. However, many fish do poorly in any amount of salt after a period of time. This includes plecotamus catfish, corydora catfish, most tetras with many of the most common ones on the list including the neon tetra, the cardinal tetra, and rummy nose tetras, elephant noses, discus fish, hatchet fish, and freshwater eels. Bettas often do well with a little salt in their water at first, but quality will decline after a couple of months because they can't live in salt water for long periods of time.

Overall, the thought is a good one, but in reality it isn't a good everyday practice. Use salt to treat some conditions and to make sure that your fish is in its best health, but don't add it to their tank all the time. The one exception to this is if you have a tank full of fish that like a little salt or could use a little salt all the time. Just make sure everyone in the tank will benefit from its use. Make sure you have an idea of what fish you have as well because you will want to keep salt in a tank with those that don't tolerate salt for one month or less and only when absolutely necessary.