How to Control Alkalinity in a Reef Aquarium

Seawater naturally contains optimal levels of calcium, bicarbonate and magnesium. These elements combine to determine the level of alkalinity. Owners of a reef aquarium must maintain the conditions that marine life are accustomed to. Reef aquarium calcium levels should be 400 to 450 parts per million. Alkalinity levels should be 2.5 to 3.5 milliequivalents per liter -- or 7 to 10 degrees of carbonate hardness. Calcium levels above 500 cause the alkalinity level to decrease and levels below 400 cause it to increase. Both extremes result in pH level fluctuation that affects the water̵7;s buffering capacity.

Things You'll Need

  • pH testing kit -- available at aquarium stores
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Instructions

    • 1

      Use the pH testing kit to monitor the alkalinity level daily. These kits contain dye that changes color depending on the pH level. Match the color of the water to the colors on the chart provided, to determine whether the level is too high or too low.

    • 2

      Clean the aquarium on a regular basis. Remove old food and aquarium waste from the tank, and change out the water frequently.

    • 3

      Introduce kalkwasser into the aquarium to raise pH levels and reduce phosphate levels. Kalkwasser is a solution of made up of calcium hydroxide and water -- about 1 to 2 teaspoons of calcium hydroxide for each liter of water. Add the solution slowly, because it has a high pH level and could cause alkalinity. Use kalkwasser for medium or large aquariums, and combine it with a reef buffer for best results. The buffer maintains pH levels and replenishes minerals needed for marine life to survive.

    • 4

      Use calcium chloride or a balanced compound as an alternative to kalkwasser. It's best to use calcium chloride for small aquariums or aquariums with a small population of marine life. Use the solution with a reef buffer for best results. The balanced compound is a dry or two-part liquid solution that maintains both calcium and alkalinity without the buildup of harmful compounds.

    • 5

      Install a calcium reactor inside the aquarium to automate the control of alkaline and calcium. The reactor is a container filled with calcium carbonate and carbon dioxide, which circulates through the tank as needed. Setting up a reactor can be expensive, but after initial setup you can maintain alkalinity levels without much effort.

    • 6

      Use common household ingredients, if funds are limited. Add 6 milliliters of unflavored seltzer per gallon of water or 1 milliliter of distilled white vinegar per gallon. Both substances immediately reduce high pH levels, so add them to the tank slowly.