What to Do to Decrease Alkaline Content in My Fish Tank

The alkalinity in fish tanks refers to the pH range on an acid/base scale, and there are several ways to lower the alkalinity using both synthetic and organic methods. A normal pH range for a freshwater tank is between 6.5 and 7.5, which is a range just on either side of neutral pH of 7. A target pH range for marine tanks is between 8.1 and 8.4. Before changing the pH in an aquarium, use a pH test strip kit to determine how much of a change is needed.

  1. Synthetic Treatments

    • Synthetic pH decreasers, such as acid additives, buffers and conditioners, are chemicals that lower the alkalinity of tank water. Many synthetic treatments are made strictly for either freshwater or marine tanks, even though they act in similar ways to reduce the alkalinity. Before acids can be added to reduce alkalinity, a reverse osmosis unit is used to remove the minerals and hardness in the water. Buffers bind to acids and bases, but they do not change the amount of acid or base in the tank. Before purchasing additives and treating aquarium water, be sure to rule out other factors that are causing the pH imbalance.

    Organic Methods

    • Vinegar, baking soda or seltzer water found at the local supermarket can also be used to reduce pH.

      Unlike synthetic treatments, organic methods do not involve adding chemicals but rather manipulating the environment within the tank to maintain proper pH levels. Using peat moss in the filtering system can aid in naturally reducing pH counts; however, that method also changes the tank's water color. Adding clean driftwood purchased from a fish supply store or incorporating an air stone into the tank will also reduce alkalinity. Seashell and coral skeleton create an increase in pH and therefore can be removed to reduce alkalinity.

    Preventive Maintenance

    • Because ordinary tap water is close in range to the pH required by most fish tanks, preventive maintenance can keep pH and alkalinity where they should be. Some fish hobbyists suggest a 10- to 15-percent water change weekly, along with moderating feeding amounts and keeping optimal tank population numbers. Additional prevention techniques are to check pH levels every two weeks to prevent severe changes that can be fatal to fish and to use as many organic techniques to maintain proper pH as possible to reduce the amount of chemicals added to the tank.

    Considerations

    • Whether using synthetic additives or organic ingredients, use the smallest amount possible to prevent overly stressing the fish with drastic pH changes. Checking the pH range often will reduce the range of pH you have to correct should your tank be susceptible to fluctuations. While treating the water before adding it to the tank may seem convenient, the pH will change when you add decorations and fish. To maintain a healthy tank, treat pH levels when the tank is set up with all its contents.