Proper PH of a Freshwater Fish Tank

Maintaining a consistent and appropriate pH in your freshwater aquarium is of the utmost importance to your fish's health. The proper pH for your tank will vary according to the species you are keeping and/or the ecosystem you wish to replicate. The pH scale measures the degree that your aquarium water is either acidic, alkaline, or neutral on a scale of 0 to 14, 0 being the most acidic, 7 neutral, and 14 the most alkaline. Tanks with a low pH have a more difficult time turning ammonia into less dangerous nitrites and nitrates.

  1. Proper pH for Freshwater Tanks

    • Most freshwater fish inhabit waters with a pH ranging from 5.0 to 9.0, with the majority of these inhabiting water which ranges from 6,0 to 7.5. The optimal pH level for your tank will vary, depending on the natural habitat of your fish (ponds, rivers or lakes) and the part of the world from which they come. For example, African cichlids prefer a higher pH of 7.8 to 9.0, while South American discus thrive in a low pH of 4.5 to 6.5. Having an exact pH is less important than maintaining a stable, steady pH within a healthy range.

    How to Maintain pH

    • To find out if your water has the ability to resist changes in pH, you first need to determine what is known as "buffering capacity." To do that, you must measure "hardness," which looks at the concentration of calcium carbonate. Aim for a reading of at least 75 mg/L, but 100 to 200 mg/L is better. Having a proper buffering system will assure that once you reach your optimal pH, your tank will maintain it. Performing routine water changes, vacuuming your gravel, keeping filters clean and running correctly and not overstocking your aquarium will help keep your buffering capacity high. Adding crushed coral or limestone to your substrate or filtration is another way of raising buffering capacity. Chemical additives sold in pet stores also will help raise the buffering capacity of your water.

    How to Change pH

    • Pet stores also sell additives which will help raise pH levels in your aquarium. Increasing the water flow and movement in your tank also will raise the pH.

      Lowering the pH can be more difficult, as you first need to remove some of your tank's buffering capacity, or soften the water in your tank. This can be accomplished by adding peat to your power filter or substrate, or by using purified tap water that has had most of its natural minerals and salts removed or reverse osmosis water. Driftwood can naturally lower pH. Whatever method you use, never allow your pH or buffering capacity to change too quickly. If you do, you risk causing stress to your fish or even killing them.