One of the topics that is constantly debated among freshwater aquarists is what role, if any, should salt play in successful aquariums. For every person who adamantly declares that every aquarium should routinely have salt added there is another person who argues that you should never add salt to a freshwater aquarium. A third group of people state that salt should only be used as treatment for specific problems while a fourth group throws up their hands in despair not knowing what to think anymore. At Segrest Farms, this is our philosophy on the subject, and please note that some of this will be perhaps over simplified to not scare away those who are chemistry averse.

The number one reason for disease and fish loss is stress. Many things can contribute to fish stress including overcrowding, poor nutrition, handling during shipping and purchasing, and poor water quality. Fish have evolved to have a natural slime coating which inhibits the entry of disease organisms (acting as a first line of defense for their immune system), acts as a lubricant to aid in movement through the water, and plays an important role in osmoregulation. When fish get stressed, the production of this slime coat is severely reduced leaving them susceptible to a plethora of problems.

Perhaps the most misunderstood of these roles is that of osmoregulation, which is basically the flow of water between an organism's cells (in this case our fish's cells) and the environment surrounding it (the water they live in) in an attempt to achieve equilibrium. However, the cells of a freshwater fish's body naturally contain a greater concentration of salt than does the surrounding water. The cells try to absorb water molecules in an effort to dilute the salt content and equalize the salt concentration between the cells and the water. Unfortunately, this is too much water for the fish to absorb, causing the fish to excrete excess water as urine through the kidneys in order to avoid over hydrating.

This is where the first benefit of adding aquarium salt comes into play. While the fish's slime coating plays a major role acting as a natural buffer against this extra hydration, when stressed, the slime coat diminishes and loses part or all of this protection. By keeping the salt concentration of the water in our tank higher, we minimize the salinity difference and can help reduce this Osmotic Stress.

Salt also helps protect against many protozoan parasites, such as Ich, Costia, Trichodina, and Chilodonella as well as flukes and other ectoparasites. Most parasites have a much lower concentration of salt in their cells than fish do, so by adding salt to the water, you can actually reverse the osmotic flow. This causes water to be drawn out of the parasites, dehydrating the organisms. Because fish have even higher salt concentrations, this elevated salt level has no adverse affects on them.

Because of these benefits, we recommend maintaining some level of salt in all aquariums (the exact level will depend based on exactly what you are planning on keeping, so do research on your specific species). However, "salt" includes not only the salt we normally think of (Sodium Chloride), but also other salts such as carbonates, bicarbonates, magnesium, potassium, and sulfates. These will all be affected by various sources, including your water source and certain substrates or decorations such as those made from crushed coral, aragonite, or a number of different rock decorations that may release minerals into the water such as limestone. This is also why a number of different salts (such as standard Aquarium Salt, Cichlid Salt, and Marine Salt) are offered in order to supply a different ratio of specific minerals to the water.

With all of these different materials affecting the chemical makeup of the water in your aquarium, you do want to keep an eye on the salinity, and the easiest method of monitoring this is through regular testing with a TDS Pen. If you need to raise your TDS level, you can do so by adding salt to the water. For most freshwater aquariums, standard aquarium salt should be the ideal choice, though there are some who swear by using marine salt in order to supply the extra minerals present. Salt concentrations can change as the result of adding water to your aquarium (such as in a water change, which will lower the salt concentration), or as the result of evaporation (which removes water but not salt, raising the salt concentration). Keep a log of these test readings to easily track changes or spot problems before they get out of hand. As with most aspects of fish keeping, stability is perhaps the most vital part of long term success.