What is the optimum pH range for plant species in aquaculture water?

• A. 7
• B. 8-9
• C. 8.5-10
• D. 5.5-6.5

Answer: (D)

pH controls how nutrients dissolve and are taken up by plant roots in water. In a slightly acidic environment, around 5.5 to 6.5, many essential micronutrients—like iron, manganese, and boron—remain more soluble and available to plants, supporting better growth and chlorophyll production. This range also helps keep ammonia in the less-toxic ammonium form (NH4+), which is gentler for fish in mixed aquaculture systems and still usable by plants. If the water becomes more alkaline, nutrients can precipitate or become less accessible, leading to deficiencies and slower plant growth. While some plants tolerate neutral to mildly acidic conditions, the 5.5–6.5 window provides a practical balance for a wide range of aquatic plant species used in aquaculture, making it the most favorable overall.