What pH does to fish and water — and how to adjust it

pH strongly affects water quality and aquatic life. The general target is pH 7.5–8.5, slightly alkaline. Low pH makes phosphate fertilizer fail permanently; high pH makes it fail temporarily. Higher pH increases the share of toxic ammonia; lower pH turns sulfide into extremely toxic hydrogen sulfide. Extreme pH lowers fish metabolism and blood oxygen affinity, reduces feed intake and growth; at hatch, pH near 10 can disintegrate eggs, and near 6.5 embryos mostly deform. Deep-silt or hypoxic ponds often run low pH; hot sunny weather with dense phytoplankton can push pH very high in a short time. Adjustment: remove excess silt and use quicklime when clearing ponds (e.g. 20–30 kg quicklime per 667 m² at 1–2 m depth for acidic water); aerate frequently, especially in hot seasons, to mix upper and lower layers; combine organic and inorganic fertilization; avoid using polluted water.