How to Lower Calcium in an Aquarium

Calcium is an important building block for a wide variety of aquarium life but especially for many corals and invertebrates. Low calcium levels can be dangerous, especially if you have a lot of marine life that depends on calcium, but too much calcium also can be dangerous. Generally, anything about 550 parts per million of calcium is recommended against, though that number will vary, depending on the marine life that you keep in your aquarium.

Things You'll Need

  • Small bucket
  • Calcium tester
  • Water
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Instructions

    • 1

      Open the aquarium and take out full buckets of water until you have taken out about 10 percent of the aquarium water.

    • 2

      Replace the water you removed from whatever water source you use, such as the tap.

    • 3

      Allow several minutes for the new water to circulate in with the old water, and then retest the calcium levels. Continue removing tank water and adding fresh water until the calcium levels have reached an acceptable level for the marine life that you keep.

    • 4

      Check levels of other important nutrients that you supplement the aquarium with. Taking out tank water will lower calcium levels along with the nutrient levels of any other tank supplement, and you may need to bring those other nutrients back in to acceptable ranges.