In daytime, during photosynthesis, phytoplankton removes CO2 from water thus causing an increase in the pH and the reverse during the night, where plants produce CO2 by respiration. Carbon Dioxide Carbon dioxide in water is a product of fish and plankton respiration and also a byproduct of organic matter decomposition. Adequate levels of carbon dioxide are necessary for phytoplankton photosynthesis especially where phytoplankton provide the main source of food and oxygen to the system. Water from underground resources is usually characterized by elevated CO2 levels and thus requires special treatment before being rendered suitable for aquaculture. Ammonia and Nitrite Low levels of ammonia and nitrite in water are sufficient to inhibit growth and threaten the survival of the fish.
Ammonia is a byproduct of fish metabolism and the decomposition of organic matter.
It exists in water in two forms, ionized and un-ionized. Un-ionized ammonia concentration is directly related to pH levels in water. Higher pH levels raise NH3-N concentration in water, increasing its level of toxicity to fish. Un-ionized ammonia toxicity causes osmoregulation imbalance, kidney failure, and gill damage. Nitrification occurs in two steps.