How to Raise pH Levels in Aquarium Water

Written by sarah goodwin-nguyen
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The pH of an aquarium is measures on a scale from 0 to 14. On this scale, 0 is acidic, 7 is neutral, and 14 is alkaline. Depending on the species being kept or the ecosystem being re-created, freshwater tanks generally run close to neutral, while saltwater needs to be slightly more alkaline. Ocean water has a pH between 8 and 8.4, depending on the location. Keeping a consistent and appropriate pH in your fish tank is more important than achieving an exact pH. However, if your aquarium runs too acidic, there are steps you can take to raise your alkalinity.

Skill level:
Moderately Easy

Things you need

  • Gravel vacuum
  • Crushed coral or limestone
  • Chemical additive to raise buffering capacity
  • Strong pump
  • Aerating device
  • Chemical additive to raise pH

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  1. 1

    Perform water changes. You can change up to 30 per cent of your water volume at one time, vacuuming your substrate well. For a freshwater aquarium, use dechlorinated tap water instead of R.O. (reverse osmosis) or distilled water, since tap water has a more alkaline pH.

  2. 2

    Raise your tank's "buffering capacity." Buffering capacity refers to your aquarium's ability to maintain a stable pH. This is accomplished by making sure your filters are clean and your filtration devices are working properly. Adding crushed coral or limestone to your substrate or in your filters is also said to raise a tank's buffering capacity. Lastly, you can purchase chemical additives which are designed to raise buffering capacity.

  3. 3

    Turn up your pumps or replace them with pumps that create a stronger water flow. Add aerating devices, and rearrange your decorations and equipment to rid your tank of "dead spots" where there is no flow. Fast-moving, well-aerated water has higher pH than slow-moving and deoxygenated water.

  4. 4

    Remove driftwood from your tank. Driftwood lowers pH in an aquarium.

  5. 5

    Add a chemical pH raiser such as "pH-Up." Follow the dosage instructions on the packaging according to your tank's water volume.

Tips and warnings

  • An aquarium with a high bio-load (more living things, like fish and plants) will usually have lower buffering capacity and pH than a more reasonably stocked one.
  • Changing the pH level too quickly causes stress to your fish.

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