High pH and alkalinity levels will complex copper, helping to reduce its toxicity. The dissolved oxygen test is one of the most important in aquaculture. Dissolved oxygen levels can affect fish respiration, as well as ammonia and nitrite toxicity. Salinity and temperature are both factors that affect dissolved oxygen levels. Closely related to alkalinity and pH, sufficient hardness levels can decrease ammonia and pH toxicity.
Calcium is also necessary for proper egg and fry development.
High nitrite levels, combined with low chloride and dissolved oxygen concentrations, may result in methemoglobinemia, better known as brown blood disease. One of the most common water tests, pH is a measure of the acidity or basicity of the water. The greatest concern with pH is how it affects the toxicity of many other substances, including nitrite and ammonia. Phosphates enter the water supply from many sources, including agricultural runoff and sewage. Although phosphorous is an essential nutrient for bone formation and is a primary ingredient in fertilizers, excessive levels can promote an overabundance of algae.