Benthic Sludge & Black Soil Remediation: Eliminating Hydrogen Sulfide (H2S) Gas & Anaerobic Pond Odor

1. The Chemistry of Black Mud & Hydrogen Sulfide Gas Formation

As intensive culture progresses beyond DOC 45, accumulating organic matter (dead plankton, unconsumed feed pellets, shrimp feces) settles onto the pond bottom, exceeding the sediment natural aerobic degradation capacity.

As dissolved oxygen is exhausted in the top 2 millimeters of sediment, obligate anaerobic sulfate-reducing bacteria (Desulfovibrio spp.) reduce abundant sulfate (SO4²-) present in brackish water into hydrogen sulfide (H2S). H2S reacts with ferrous iron to precipitate ferrous sulfide (FeS), turning the soil jet-black.

Even trace concentrations of unionized H2S (as low as 0.01 mg/L) cause permanent damage to shrimp gill lamellae and disrupt mitochondrial ATP synthesis.

2. Oxidation-Reduction Potential (ORP) & Safe Ecological Thresholds

Pond managers should monitor sediment ORP using a platinum electrode mV meter:

• Safe Aerobic Zone: +100 mV to +300 mV (clean sediment, active nitrification)

• Cautionary Hypoxic Zone: 0 mV to -100 mV (sludge accumulation begins)

• Lethal Anaerobic Danger Zone: -150 mV to -300 mV (active H2S generation, massive shrimp mortality risk)

3. The Next Sludge Deep-Bed Sand Method

Because standard liquid probiotics float in the water column without penetrating deep benthic mud, Next Farm Bio Sciences engineered the Deep-Bed Sand Method:

• Take 3.0 to 5.0 Litres of Next Sludge per acre.
• Mix thoroughly with 25 to 50 kg of clean, dry river sand or zeolite granules in a wide plastic tub.
• Allow 15 minutes for the specialized spore-forming Bacillus and Thiobacillus consortia to absorb onto the sand surfaces.
• Broadcast directly over known sludge accumulation zones (pond center and aerator dead corners) during bright morning hours.
• The dense sand carries the biological consortium directly to the benthic interface, rapidly digesting organic sludge in situ.