How to Increase the Alkalinity in an Aquarium With Buffering and CO2

Alkalinity or carbonate hardness is the measure of water's ability to prevent a drop in pH. Alkalinity comprises the negative ions, carbonate (CO2-3) and bicarbonate (HCO-3), both of which react to neutralize the hydrogen ions associated with acids. Alkalinity constantly decreases in closed systems, as the fish and invertebrate animals produce acid through their metabolism. As the presence of carbon dioxide (CO2) drives alkalinity down, it is important to rid the aquarium of carbon dioxide, on an ongoing basis.

Things You'll Need

  • Reliable alkalinity test kit
  • Protein skimmer for salt water aquarium
  • Buffering powders
  • Higher algae and living corals for salt water aquarium
  • Calcium hydroxide solution
  • Fan (optional)
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Instructions

    • 1

      Ensure that your alkalinity test kit is accurate. A low alkalinity reading may be caused by old reagents in the test kit.

    • 2

      Install a protein skimmer on your seawater tank. Protein skimmers, or foam fractionators that are functioning correctly and are large enough for the aquarium volume, will drive off excess carbon dioxide from the water.

    • 3

      Add buffer powders to the aquarium on a weekly basis, in order to raise the alkalinity. These powers contain carbonate and bicarbonate ions that counter the hydrogen ions that force the alkalinity down.

    • 4

      Encourage the growth of higher algae and include living corals in the seawater aquarium. The zooxanthellae living within the coral polyp tissue, makes use of carbon dioxide, which lowers alkalinity, in order to photosynthesize.

    • 5

      Use calcium hydroxide solution in the place of tap water, when replacing water that has evaporated. As the calcium hydroxide combines with excess carbon dioxide in the water, bicarbonates and carbonates are produced and the alkalinity is boosted.

    • 6

      Open a window if your aquarium is standing in a confined room. Air exchange with the outside is minimal in most modern homes and carbon dioxide in the air is therefore typically high. Gas burning stoves, cigarette smoking and respiration from people and companion animals, all contribute to high carbon dioxide levels. These elevated levels cause the alkalinity and pH to drop.

    • 7

      Place a fan in the room with your aquarium, to create better air circulation and to dispel carbon dioxide in the air, which can be absorbed into the aquarium.

    • 8

      Move the aquarium to another room, if there is insufficient air circulation and carbon dioxide retention in the area where it is standing.

      Do not overstock your aquarium, as fish and invertebrate animals give off carbon dioxide through respiration.