Best Time to Test Dissolved Oxygen in Fish Ponds with Qiwei JPB-70A Malaysia
Best Time to Test Dissolved Oxygen in Fish Ponds with Qiwei JPB-70A Malaysia
Dissolved oxygen in a fish pond changes throughout the day. Testing only when it is convenient may produce a result that does not reveal the pond’s most critical oxygen condition.
The Qiwei JPB-70A Portable Dissolved Oxygen Meter allows fish farmers to measure DO at different times and identify daily oxygen patterns before they affect feeding, growth or fish survival.
Why Does Dissolved Oxygen Change During the Day?
Algae and aquatic plants produce oxygen through photosynthesis when sufficient sunlight is available. At night, photosynthesis stops, but fish, plants and microorganisms continue consuming oxygen.
A typical daily pattern may be:
Before sunrise: Dissolved oxygen is usually at its lowest
Morning: Oxygen begins increasing as sunlight becomes stronger
Afternoon: Oxygen may reach its highest level
After sunset: Oxygen production stops and the level begins falling
Weather, stocking density, feed, algae and aeration can change this pattern.
Most Important Time: Before Sunrise
Early morning is often the best time to identify a pond’s minimum dissolved oxygen condition.
Testing only in the afternoon may be misleading. A pond showing a high afternoon reading can still experience dangerously low oxygen before sunrise.
Use the JPB-70A before sunrise when:
Fish stocking density is high
Fish are approaching harvest size
Feeding rate has increased
The pond contains heavy algae growth
Several cloudy days have occurred
Fish have shown abnormal behaviour
Early-morning mortality has happened
Aerator performance is uncertain
Record the measurement time accurately so that results can be compared from day to day.
Test Before Feeding
Fish may reduce their feeding activity when oxygen is insufficient. Adding more feed under poor conditions can increase waste and place additional demand on the pond.
A pre-feeding DO check helps operators decide whether to:
Feed normally
Reduce the feeding quantity
Delay feeding
Start aeration
Investigate another water-quality problem
The appropriate action depends on the species, fish size and farm-management procedure.
Test During Late Afternoon
An afternoon reading helps show how much oxygen has accumulated during daylight hours.
Compare the afternoon result with the following early-morning measurement. A large overnight decrease may indicate:
Heavy biological oxygen demand
Excessive algae
High stocking density
Too much organic matter
Insufficient night-time aeration
Repeated morning and afternoon readings provide more useful information than an isolated measurement.
Test After Heavy Rain
Rain can affect:
Water temperature
Pond mixing
Algae activity
Surface runoff
pH
Organic loading
Oxygen distribution
After heavy rain, measure dissolved oxygen at several locations and depths. Do not assume that the entire pond has the same condition.
Test During Cloudy Weather
Several cloudy days can reduce photosynthesis and daytime oxygen production.
Increase monitoring frequency when:
The sky remains overcast
Rain continues for several days
The pond has dense algae
Fish biomass is high
Aeration capacity is limited
An acceptable reading on the first cloudy day does not guarantee that oxygen will remain sufficient later.
Test After Increasing Feed
As fish grow, farms normally increase feeding. More feed can lead to:
Higher fish respiration
Additional waste
More uneaten feed
Greater microbial activity
Increased oxygen consumption
Measure DO more frequently after a significant increase in feed or stocking biomass.
Test Before and After Aeration
The JPB-70A can help assess whether an aerator is improving pond conditions.
Recommended procedure:
Measure DO at several points before starting the aerator.
Record the location, depth and time.
Operate the aerator for a consistent period.
Repeat the measurements at the same points.
Compare the results.
Check whether oxygen improvement reaches areas away from the aerator.
A high reading close to the aerator does not confirm even distribution across the pond.
Establish a Practical Testing Schedule
A basic monitoring schedule may include:
SituationSuggested MeasurementNormal routine operationEarly morning at consistent locationsHigh stocking densityEarly morning and late afternoonExtended cloudy weatherMore frequent checksHeavy rainAfter conditions are safe for testingFish behaving abnormallyImmediatelyFeeding increaseBefore feeding and during follow-upAerator adjustmentBefore and after operationNear harvestIncrease monitoring frequency
The exact schedule should follow the farm’s operating needs and risk level.
Use Consistent Measurement Locations
For meaningful comparisons, keep the following consistent:
Pond identification
Testing point
Probe depth
Measurement time
Probe movement
Aerator condition
Recording method
Marking regular measurement points can reduce variation between different operators.
How to Use the Qiwei JPB-70A
Inspect the membrane and electrode.
Switch on the meter and allow the probe to prepare.
Lower the electrode into the water.
Keep it away from mud and large air bubbles.
Move the probe gently through the water.
Wait for a stable reading.
Record the DO value and temperature.
Repeat at other locations.
Rinse the probe after testing.
Because the JPB-70A uses a polarographic electrode, gentle water movement across the membrane is important.
JPB-70A Main Specifications
Dissolved oxygen range: 0.0–19.9 mg/L
Resolution: 0.1 mg/L
Basic DO accuracy: approximately ±0.3 mg/L
Temperature range: 0–40°C
Automatic temperature compensation
Portable polarographic dissolved oxygen electrode
These specifications are suitable for routine pond monitoring and general field spot checks.
Keep a Daily Pond Record
Record:
Date
Time
Pond number
Measurement location
Probe depth
DO result
Water temperature
Weather
Feeding quantity
Aerator operating time
Fish behaviour
Corrective action
Trend records make it easier to identify gradual deterioration before a serious event occurs.
Buy Qiwei JPB-70A in Malaysia
The Qiwei JPB-70A Portable Dissolved Oxygen Meter is available from MTM Precision in Malaysia for fish ponds, shrimp farming, hatcheries, wastewater and general water-quality testing.
Contact us for current price, stock, accessories and product-selection advice.
Contact MTM Precision
MTM Precision Sdn. Bhd. (744811-A)
Telephone: +603-8080 7172
WhatsApp: +6016-660 7346
Email: mtmpre@yahoo.com / enquiry@mtmpre.com.my
Website: www.mtmpre.com.my
Showroom & Service Centre
No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia.
Contact MTM Precision for the Qiwei JPB-70A dissolved oxygen meter price and availability in Malaysia.
18 Sep 2026
