In shrimp and fish farming to increase production, it must be raised with high density and fed a lot. The amount of food along with the waste of shrimps and fishes forming toxic gases H2S, NH3 and NO2 arises continuously and often reaches the level of toxic to animals quickly after only one month of raising. In these toxic substances, H2S is the most dangerous.
During the culture process, food residues and wastes are most deposited in the pond bottom. This deposition layer is divided into 2 parts. The upper part is very thin, the color is brighter, easily lost under the impact of water flow and farming activities of farmers. The lower layer is rich in organic matter, darker color, lack of oxygen so active anaerobic bacteria produce a lot of H2S. H2S toxin is much larger than NH3 and NO2, only 0.01 ppm (10-8) in the aquarium has caused mass mortality.
In addition to microbial decontamination methods and biofloc production, the use of activated carbon is a sustainable measure. Activated carbon from rice husk with many small pores can adsorb poisons, create a substrate for beneficial bacteria to function. In addition, the deposited rice husk layer reinforces the bright mud above, forming a barrier to prevent H2S from entering the water, causing shrimp death.