The pH of catfish ponds varies with the time of day, with lowest values in the early morning and highest values in the late afternoon. This means that the toxicity of the chlorine compounds formed by the reaction of bleach or HTH with pond waters is greatest in the early morning and decreases through the day. The pH of most fish ponds is usually greater than 7.5. Types of chlorine compounds that may be present in fish ponds. Many of the chlorine compounds that result from the reaction of bleach or HTH with water can effectively oxidize organic matter in fish ponds.
Fish ponds have abundant organic matter in both living and dead form.
Living forms of organic matter in fish ponds include algae, bacteria and other micro-organisms. Dead forms of organic matter include dead algae and fish fecal solids. Many of the living forms of organic matter are critically important to the maintenance of water quality favorable for fish production. Algae and bacteria are important regulators of oxygen and ammonia concentrations in fish ponds. The reaction of the various chlorine compounds with organic matter is not selective.