Quick answer
Most farmers run aeration 24/7 "to be safe" - and pay for it. The short version: turn it off only when dissolved oxygen is confirmed above 5 mg/L and no risk event is coming - typically low-density ponds in the mid-afternoon DO peak. Never turn it off at night, before feeding, before storms, during molting, or during stress. Better than on/off: run variable speed (VFD) to match the DO curve and cut 15-25% of power without ever risking the crop.
Why "always on" is wrong
- Aeration is typically 60-70% of a shrimp pond's electricity bill in tropical markets.
- Full-speed 24/7 burns energy at times DO is already 6-8 mg/L (the mid-afternoon photosynthesis peak).
- Over-aeration also cools the pond, increases evaporation, and can re-suspend sediment in shallow ponds.
- The goal is a DO floor (at least 3 mg/L at all times, 5+ mg/L for growth), not maximum DO.
Aeration is not a switch you flip when fish look stressed - it is a production tool with a schedule. The question is not "should I run it?" but "when does running it stop paying for itself?"
The DO daily curve (the mental model)
| Period | Photosynthesis | DO trend | What to do |
|---|---|---|---|
| 06:00-12:00 | Ramping up | Climbing | Can reduce speed gradually (with VFD) |
| 12:00-16:00 | Peak | Mid-afternoon peak 6-8 mg/L | The only "off / minimum speed" window |
| 16:00-20:00 | Fading | Falling | Return to full speed |
| 20:00-04:00 | None | Steady decline | Full speed, never off |
| 04:00-06:00 | None | Dawn minimum (danger point) | Full speed + check |
This curve is why the classic mortality event happens at dawn: photosynthesis stops at sunset, respiration continues all night, and DO bottoms out at 04:00-06:00. If your aeration strategy is "on when I remember," that is exactly when you are most exposed.
Two DO checks a day: the only tool you really need
You do not need an expensive controller to run the DO-curve schedule. A handheld dissolved-oxygen meter, checked at two fixed points every day, is enough for most farms:
- Dawn check (05:00-06:00) - the daily minimum. If it stays above 3 mg/L here, your overnight aeration is correct.
- Mid-afternoon check (14:00-16:00) - the daily maximum. If it reaches 5-6 mg/L, you have a real window to reduce power.
Keep three days of readings before changing anything. If the dawn minimum is tight (2.5-3 mg/L), do not cut a single minute of night aeration - fix the equipment or reduce stocking first. The schedule below assumes your dawn minimum is healthy.
A sample day on a 10-mu shrimp pond
| Time | Action |
|---|---|
| 20:00-06:00 | Full speed (non-negotiable night coverage) |
| 06:00-08:00 | Stay at full speed while DO recovers from the dawn minimum |
| 08:00-12:00 | Reduce to 70-80% speed as photosynthesis builds DO |
| 12:00-16:00 | Reduce to 50-70% speed, or off only if DO is confirmed 5+ mg/L |
| 16:00-20:00 | Back to full speed before sunset |
| Storms / molting / treatment days | Full speed 24 h, ignore the schedule |
This pattern alone - keeping the afternoon window but never touching the night - typically cuts 10-20% of electricity with zero added mortality risk, before you even consider a VFD.
5 times you must NEVER turn it off
1. Night (20:00-06:00) - photosynthesis stops; DO falls toward the danger zone (2 mg/L). Dawn (04:00-06:00) is the classic mortality window.
2. Around feeding (1-2 h before and after) - feed digestion consumes oxygen and shrimp activity spikes.
3. Before storms / heavy rain / overcast days - barometric pressure drops, algae die off, and sudden temperature swings collapse DO fast.
4. During molting peaks (around full/new moon) - shrimp are weaker and need more oxygen, not less.
5. Any stress event - disease treatment, harvest preparation, sudden temperature change, transport.
When it IS safe to cut back or off
- Low-density ponds (under about 8-10 shrimp per m2, or 60,000/ha) with confirmed DO above 5 mg/L in mid-afternoon: a 1-2 hour afternoon window is low-risk.
- Off-season / winter low-density ponds in mild climates: partial shutdown is possible with a DO meter.
- Key condition: you must have a reliable DO measurement - a handheld meter checked at the dawn minimum and mid-afternoon, not guesswork.
- Rule of thumb: reduce power, not full stop. Cut to 50-70% speed in the afternoon window instead of off, unless DO is clearly 5+.
Smarter than on/off: variable speed + DO control
- VFD blowers let you follow the DO curve automatically: full speed 20:00-06:00, ramped down mid-afternoon.
- Realistic savings: 15-25% electricity vs fixed-speed 24/7 - without any shutdown risk.
- Sensor + controller setup: an optional DO probe helps; for most farms under about 30 mu, a handheld check twice a day is enough; full automation pays off for bigger operations.
3 common mistakes
1. Turning off at night "to save power" - the exact time DO collapses, and the largest cause of unexplained morning losses.
2. Turning off before a storm - storms are when DO crashes fastest, not slowest.
3. Treating aeration as all-or-nothing - no middle setting, missing VFD as the cost-saving middle option.
FAQ
Q: Can I turn off aeration at night in shrimp ponds? A: No. Photosynthesis stops at night and DO falls continuously; the 04:00-06:00 window is the highest mortality risk. Keep full aeration 20:00-06:00.
Q: When is dissolved oxygen highest during the day? A: Mid-afternoon (14:00-16:00), when photosynthesis peaks; this is the only realistic window to reduce or pause aeration, and only if DO is above 5 mg/L.
Q: How much can variable speed save? A: 15-25% of aeration electricity vs fixed-speed 24/7, because you run full speed only when needed.
Q: Does rain lower dissolved oxygen? A: Yes - pressure drop, algal die-off and surface cooling can crash DO within hours. Never stop aeration before or during storms.
Q: What is the minimum dissolved oxygen for shrimp? A: Keep at least 3 mg/L at all times; below 2 mg/L shrimp stress and mortality rise fast. Target 5+ mg/L for growth.
Q: Is it better to reduce speed than turn off? A: Usually yes. Cutting to 50-70% speed in the afternoon window keeps a safety margin; full stop is only for low-density ponds with confirmed DO above 5 mg/L.
Conclusion
The difference between a profitable shrimp season and a disaster is often not the equipment - it is the schedule. Run aeration to the DO curve: full speed through the night and dawn, reduced or off only in the confirmed afternoon peak, and never off during feeding, storms, molting or stress. If you want to save without risk, add variable speed.
Not sure when to cut power on your farm? Send us pond size, species and stocking density - our engineers reply within 24 hours with a blower + schedule recommendation. Contact us
Related reading: Aquaculture Aeration Equipment Guide | Reduce Aeration Energy Costs in Tropical Shrimp Farming | Roots Blower Sizing: Step-by-Step Calculation | Browse roots blowers with VFD
