In intensive aquaculture ponds,fish metabolism and bacterial nitrification are the main formation of acids.
The quantity of hydrogen ions (H+) in water will determine if it is acidic or basic. A value of 7 is considered neutral and values below 7 are considered acidic;above 7, basic.Most fish can tolerate a pH range of 5-10; however,a range of 6.5-8.5 is perferred for most aquaculture species.
A buffering system to avoid wide swings in pH is essential in aquaculture.without some means of storing carbon dioxide released from plant and animal respiration,pH levels may fluctuate in ponds from approximately 4-5 to over 10 during the day. Figure 3 shows the reason for the change of PH in culture tanks. In recycling systems constant fish respiration can raise carbon dioxide levels high enough to interfere with oxygen intake by fish,in addition to lowering the pH of the water. To replace lost alkalinity and sustain the buffering capacity of water,one of the most important substance is carbonate in the form of limestone,bicarbonate of soda,or other common sources is added often, bio-filter media (oyster shell) or some other components of system (concrete tanks) serve as a source of carbonates.Depending on the species cultured, frequent monitoring of water hardness,alkalinity and pH are required.To avoid fluctuate of pH levels,carbonate substance or recycling water is required