There are plenty of sites that explain what pH is (the power or potential of Hydrogen and it’s logarithmic formulation). How it is measured (using test strips [chemical], titration [reaction] or meters [electronic comparison] to measure the acidity or alkalinity of a solution, numerically equal to 7 for neutral solutions, increasing with increasing alkalinity and decreasing with increasing acidity). The pH scale commonly in use ranges from 0 [Acidic] to 14 [alkaline]. Its importance in gardening and aquaculture (Many nutrients and minerals can only be absorbed by the plants and/or used by the fish within a specific pH range. Different cultivars and aquatic species do better in different ranges of pH).

The pH of water or a nutrient solution determines the solubility (the amount that can be dissolved) and biological availability (amount that can be utilized by plant and aquatic life) of chemical constituents such as nutrients (phosphorus, nitrogen, and carbon) and minerals and heavy metals (calcium, potassium, lead, copper, cadmium, etc.). pH also determines whether plants and aquatic life can use them, or the degree to which they are soluble determines their toxicity. Metals tend to be more toxic at lower pH because they are more soluble.

If one is interested in delving deeper into these aspects of pH, I would suggest doing a search on the Internet. Wikipedia.org has an in depth article, Britannica.com has additional information and Google.com can lead to a complete understanding of the chemistry of pH.

This article is aimed at the practical side of pH and how it relates specifically to hydroponic, aquaponic and aquaculture production. What pH levels should be used for optimum production of both plants and fish? How to adjust or correct pH levels when they are out of range? How often should the pH be adjusted? What specifically can be used to adjust pH levels? What are the pros and cons of the different materials available for pH adjustment? What problems within a system may be pH intolerance specific? How to recognize indicators of pH intolerance

What pH levels should be used for optimum production of both plants and fish?


Recommended pH levels for optimum production of plants and fish
Hydroponic Plants
The best pH range for hydroponic plants is from 5.8 to 6.8, 6.3 being ideal. Roots take in nutrients at different rates and this may cause the ratios of nutrients in solution to change the pH. When the pH level is below 5.0 or above 7.5, plants are not able to absorb some nutrients. Proper pH must be maintained for the best nutrient absorption and optimum growth. pH should be checked regularly, daily is not too often. The pH may fluctuate up and down, based on plant nutrient use, environmental conditions, grow mediums, and the type of hydroponic system. As long as the pH level does not change more than one full point (5.3 to 7.3), it should have a minimal affect on nutrient uptake.