1. Important Safety Instructions
Please read and understand all safety instructions before operating this product. Failure to follow these instructions may result in product damage, injury, or electric shock.
- Always ensure the heater is fully submerged in water before connecting it to a power source.
- Ensure proper water circulation around the heater for optimal performance and safety.
- After turning off the heater, allow it to cool in the aquarium water for 15-30 minutes before removing it. This prevents the residual heat from potentially damaging the protective shell.
- Do not place the aquarium heater directly into sand or mud, as this can lead to inaccurate temperature readings and inefficient heating.
- Keep this product out of reach of children.
- Inspect the power cord and heater for any damage before each use. Do not use if damaged.
- This appliance is intended for indoor use only.
2. Product Overview
The AQQA 300W Aquarium Heater is designed to maintain a stable and consistent water temperature in your aquarium. It features durable quartz heating rods for efficient heat transfer, a heat-resistant ABS protective shell, and an external digital controller for easy and safe temperature adjustment.

Key Features:
- Durable Quartz Heating Rods: Provides fast, even, and efficient heat transfer.
- Heat-Resistant ABS Shell: Offers reliable performance and anti-scald protection.
- External Digital Controller: Allows for safe and convenient temperature adjustment outside the water.
- Intelligent Overheat Protection: Automatically stops heating if water temperature exceeds 95°F (35°C).
- Dry-Run Protection: Auto power-off if the heater is not fully submerged.
- Memory Function: Automatically restores previous temperature settings after a power interruption.
- Adjustable Temperature Range: 59-94°F (15-34°C).
3. Setup
Follow these steps to properly install your AQQA Aquarium Heater:
- Attach Adhesive Pad: Clean the desired area on the outside of your aquarium tank. Stick the adhesive pad firmly onto the tank surface.
- Mount Controller Bracket: Attach the controller bracket to the adhesive pad.
- Place Controller: Securely place the external digital controller onto the mounted bracket.
- Install Heater: Submerge the heater completely in your aquarium water. Ensure it is positioned vertically or horizontally in an area with good water circulation. Use the included suction cups to secure the heater to the inside wall of the tank.
- Connect Power: Plug the heater's power cord into a suitable electrical outlet. The controller will display the current water temperature.

Important Note:
- The heater must be fully submerged at all times during operation.
- Avoid burying the heater in sand or gravel to prevent inaccurate readings and potential damage.
4. Operating Instructions
The external digital controller provides easy access to adjust and monitor your aquarium's temperature.

Temperature Adjustment:
- Unlock Controller: Long press the lock button (🔒) for 1-3 seconds to enter setting mode. The 'Set Temp' display will begin to flash.
- Set Target Temperature: Use the up (↑) and down (↓) arrow buttons to adjust the target temperature. Each press changes the temperature by 1°F/°C. The adjustable range is 59°F–94°F (15°C–34°C).
- Auto-Lock: After 3 seconds of inactivity, the system will automatically lock the settings to prevent accidental changes.
Switching between Fahrenheit (°F) and Celsius (°C):
Long press the °F/°C button for 1-3 seconds to toggle between Fahrenheit and Celsius display modes.
Memory Function:
The heater is equipped with a memory function that automatically restores your previously set temperature settings after a power interruption, ensuring consistent warmth for your aquatic pets.

Product Video:
Official product video demonstrating the AQQA Aquarium Heater's features and operation.
5. Safety Features
The AQQA Aquarium Heater incorporates advanced safety systems to protect your aquatic environment.

Overheating Protection:
If the water temperature rapidly exceeds 95°F (35°C), the LED screen on the controller will flash “EE” and the heater will automatically stop heating to prevent harm to your fish and equipment.
Dry-Run Protection:
If the aquarium heater is not fully submerged in water, the controller will display “Er” and automatically power off. This prevents the heater from operating dry, which could cause damage or fire hazards.
6. Maintenance
Regular maintenance ensures the longevity and efficient operation of your AQQA Aquarium Heater.
- Cleaning: Unplug the heater and allow it to cool completely in the water (15-30 minutes) before removing. Gently wipe the heater's surface with a soft cloth to remove algae or mineral deposits. Do not use harsh chemicals or abrasive materials.
- Inspection: Periodically check the heater and its power cord for any signs of damage, cracks, or wear. Ensure the suction cups are securely holding the heater in place.
- Water Changes: Always unplug the heater during water changes to prevent dry-run activation or accidental damage.
7. Troubleshooting
If you encounter any issues with your AQQA Aquarium Heater, refer to the following common problems and solutions:
| Problem/Error Code | Possible Cause | Solution |
|---|---|---|
| Controller displays "EE" | Water temperature exceeds 95°F (35°C) (Overheating Protection activated). | Check ambient room temperature. Ensure proper water circulation. If necessary, perform a partial water change with cooler water. The heater will resume operation once the temperature drops. |
| Controller displays "Er" | Heater is not fully submerged in water (Dry-Run Protection activated). | Ensure the heater is completely underwater. Check water level in the aquarium. The heater will resume operation once fully submerged. |
| Heater not heating / Inaccurate temperature reading | Incorrect temperature setting, poor water circulation, heater buried in substrate, or heater malfunction. | Verify the set temperature on the controller. Ensure good water flow around the heater. Reposition the heater if it's in sand/mud. If issues persist, contact customer support. |
| Controller display is off | No power or power interruption. | Check power outlet and connections. Ensure the power cord is not damaged. The memory function will restore previous settings upon power return. |
8. Specifications
Detailed technical specifications for the AQQA Aquarium Heater 300W.

| Specification | Detail (300W Model) |
|---|---|
| Model Number | GUS-AQ201-300W-US |
| Power | 300W |
| Applicable Aquarium Size | 30-80 Gallons (115-300 Liters) |
| Voltage | AC 110-120V/60Hz (US Standard) |
| Temperature Range | 59°F–94°F (15°C–34°C) |
| Temperature Accuracy | ±1°F/±1°C |
| Material | Quartz Heating Rods, ABS Protective Shell |
| Item Weight | 1.92 pounds |
| Item Package Dimensions | 13.3 x 7.4 x 2.3 inches |
9. Warranty and Support
For any questions, technical support, or warranty inquiries regarding your AQQA Aquarium Heater, please contact AQQA customer service. Refer to your product packaging or the official AQQA website for the most current contact information.
We are committed to providing high-quality products and excellent customer service.





