How to Assess Deterioration in Aquaculture Pond Bottom Quality

In aquaculture, the condition of pond bottom sediment directly impacts water quality, which is often the first indicator of underlying sediment issues. Improving pond bottom quality is essential to maintaining water quality, as pathogens tend to thrive in polluted sediments before dispersing through the water, affecting aquatic animal health. This is “Take care of the bottom to take care of the water.”

Causes of Blackened and Foul-Smelling Pond Sediment

Foul-smelling, blackened sediment is often the result of several key factors:

1.Inadequate Pond Cleaning: Incomplete or infrequent cleaning can leave organic debris that contributes to sediment decay.

2.High Stocking Density and Feed Residue: High fish density combined with excessive feed increases organic waste accumulation at the pond bottom. This material decays, causing the sediment to become hot, sticky, black, and malodorous.

3.Low Dissolved Oxygen and Anaerobic Conditions: Lack of oxygen at the bottom can lead to anaerobic fermentation, worsening sediment quality.

4.Excessive Use of Chemical Treatments: Overusing certain chemicals to treat the bottom can lead to sediment compaction and disrupt the micro-ecosystem.

Consequences of Sediment Deterioration

Degraded pond sediment negatively impacts the entire pond ecosystem and affects fish health and productivity in multiple ways:

1.Reduced Water Quality and Ecological Stability: Poor sediment quality reduces water quality, impairing the pond's overall ecological balance and productivity, and negatively impacting aquatic animals.

2.Increased Toxins and Oxygen Depletion: Degraded sediment often appears black and emits a foul odor. Fish raised in such environments experience poor activity and reduced growth rates. As water temperatures rise, organic matter decomposes rapidly, consuming dissolved oxygen and releasing harmful toxins. In severe cases, this can result in oxygen depletion, fish suffocation, or even mass die-offs.

How to Determine if Pond Sediment is Deteriorating

Here are some practical methods to assess pond bottom quality:

1.Observe Bottom Sediment Using a Rod: Insert a bamboo stick or other tool to examine sediment color and smell. Black and foul-smelling sediment indicates severe degradation.

2.Smell Odors When Using Aerators: If the aerator stirs up an unpleasant odor and produces persistent or discolored foam, sediment degradation is likely advanced.

3.Look for Rising Bubbles or Foam on the Surface: Persistent foam or “smoke-like” bubbles rising from the bottom indicates significant sediment breakdown.

4.Monitor Water Consistency and Smell: Thick, sluggish water with a sulfuric smell, especially at the pond’s downwind end, signals severe sediment issues.

5.Check pH Variation: Minimal pH fluctuation from morning to evening suggests organic buildup, as well-balanced water should have natural daily pH shifts.

6.Observe Odors from Wave Machines: If using a wave machine, a fishy or sour smell detected downwind is a clear sign of sediment problems.

7.Look for Signs of Disease in Bottom-Dwelling Fish: In mixed-species ponds, disease or mortality in bottom-dwelling fish alone often points to sediment deterioration.

Common Products to Improve Pond Bottom Quality

Effective products for restoring pond sediment quality include:

1.Biological Products: Probiotics such as Bacillus subtilis, Bacillus licheniformis, and Bacillus coagulans are commonly used, along with enzymes like protease and amylase, to break down organic matter.

2.Chemical Treatments: Products such as potassium monopersulfate compounds, ferrate salts, activators, nutrients, and adhesion agents are also effective for sediment rejuvenation.

Maintaining a healthy pond bottom is essential for water quality and the health of aquaculture stock. Monitoring the bottom regularly and using targeted treatments can help prevent or mitigate sediment-related issues, fostering a more productive and resilient aquaculture environment.