Using Sea Salt to Raise pH in a Freshwater Aquarium

A stable pH is essential for a healthy aquarium ecosystem. Almost all freshwater fish thrive at a pH between 5.5 and 7.5, but a fish's exact needs for alkalinity or acidity may vary. While some fish, such as domseticated strains of tetras, barbs, livebearers and danios, can tolerate a surprisingly broad pH range. Many healthy guppies, for example, can handle any pH between 4.5 and 8.5.

Nevertheless, even if you have a hardy species on your hands, it's important to tailor the chemistry of your fish tank to suit the individual needs of the fish in your care. Fish species that need alkaline water will experience weakened immunity, infertility and, eventually, death if they are in an unsuitably acidic environment. Similarly, fish with a preference for slightly acidic water, such as cardinal tetras, will have similar symptoms if exposed to an alkaline environment.

When to Adjust your pH

In a freshwater aquarium, pH adjustment should never be pursued as guess-work. The only way to know when to adjust your pH is to measure the pH of your aquarium using a litmus strip or other testing device. You should perform this test at least two to four times per month, especially when establishing a new aquarium. The testing device should give you a close, accurate measurement of your fish tank's pH.

If you are keeping multiple species in a non-biotope community tank, you may need to calculate the ideal range of alkalinity or acidity that will fit every species in your care. For example, if you are keeping both guppies, who prefer alkaline water, and neon tetras, who prefer acidic water, your ideal pH range will be approximately neutral, or 6.5-7.5. If your current pH is lower than necessary, sea salt is one option to raise the water's pH to an acceptable level.

Sea Salt Function

Sea salt is composed almost entirely of sodium chloride, which is the same form of salt used for culinary purposes. Although salt itself has a neutral pH, it contains several ionic minerals, such as calcium and magnesium, which have a higher pH than unaltered water. Due to dissolved minerals, ocean water itself has a pH slightly above 8, which is appropriate for saltwater and brackish-water species. Trace amounts of sea salt may increase the pH of a freshwater tank.

The amount of sea salt that you should use will depend upon the salinity tolerance of the species in your care. Add no more than one half-teaspoon of sea salt per 10 gallons of aquarium water per week, while carefully monitoring your pH with a litmus test and the specific gravity (salinity) of your tank with a hydrometer. Stop adding sea salt as soon as your readings near the salt-tolerance threshold of the species in your care, or as soon as you achieve a tolerable pH-- whichever comes first.

Dangers and Risks

The addition of sea salt to a freshwater aquarium may be harmful under some circumstances. Although some brackish-dwelling, saline-tolerant species such as the sailfin molly can tolerate salt levels as high as 1.020, some freshwater fish perish at any pH above 1.001. For this reason, it is essential that you maintain an awareness of the salt tolerance theshold for every fish in your aquarium. Improper use of sea salt can lead to the death of every fish in the tank.

Several alternatives may increase aquarium pH with fewer risks than sea salt. Most pet supply stores offer liquid mineral supplements designed to heighten the pH of your aquarium's water. Small amounts of baking soda, used carefully, can accomplish the same task. Additionally, certain ornaments, such as seashells, will harden and alkalinize your water chemistry.