Introduction
Thank you for choosing the fishkeeper 800W Aquarium Heater. This intelligent submersible heater is designed to maintain a stable and optimal temperature for your aquatic environment, suitable for 85-220 gallon freshwater and saltwater tanks. It features advanced safety mechanisms, precise temperature control, and a user-friendly external LED display.
Key Features:
- Upgraded Material for Superior Durability: Constructed with nickel-chromium resistance wire, 0.6-inch thick quartz glass, and an ASB shell for high temperature and corrosion resistance. Features triple-sealed waterproofing and a UL-certified three-pin plug with a thickened power cord for enhanced safety.
- Multiple Safety Features: Includes dual relay protection circuits, dual temperature probes, auto shut-off when out of water (E1), overheat protection (HH), low-temperature protection (LL), and abnormal temperature alerts (E2).
- Intelligent Temperature Controller: External LED display shows real-time power and water temperature. Easy temperature adjustment with two buttons and an automatic power-off feature for out-of-water conditions.
- Intelligent PID Temperature Control: Advanced PID frequency conversion technology maintains water temperature within a precise range, activating when the temperature drops 0.6°F below the set point and maintaining constant temperature when it exceeds by 0.6°F.
- Precise and Visible Temperature Regulation: Adjustable temperature range from 63°F to 93°F in 0.5°F increments. Features a power failure memory function.

The fishkeeper 800W Aquarium Heater and its external intelligent LED temperature controller.
Official product video demonstrating the fishkeeper Ultra-Safe Fish Tank Heater's features and operation.
Safety Precautions
- Always ensure the heater is fully submerged in water before plugging it in.
- Do not operate the heater if the power cord or heating element is damaged.
- Unplug the heater before performing any maintenance on your aquarium, such as water changes or cleaning.
- Keep the external controller dry and away from water splashes.
- This heater is designed for indoor use in aquariums only. Do not use it for other purposes.
- Ensure the heater is securely attached to the aquarium wall using the provided suction cups.
- Children should be supervised to ensure they do not play with the appliance.
Product Components
The fishkeeper 800W Aquarium Heater package includes:
- 800W Submersible Heating Rod
- External Intelligent LED Temperature Controller
- Suction Cups for installation
Setup Instructions
- Unpack: Carefully remove all components from the packaging.
- Position the Heater: Place the heating rod fully submerged in your aquarium. Ensure it is positioned horizontally or vertically in an area with good water circulation. Use the provided suction cups to secure it firmly to the aquarium glass.
- Connect to Controller: The heating rod is pre-connected to the external intelligent LED temperature controller.
- Mount Controller: Mount the external controller in a dry, easily accessible location outside the aquarium.
- Power On: Plug the heater's power cord into a suitable electrical outlet. The LED display on the controller will light up, showing the real-time water temperature and power.
- Allow Stabilization: Allow the heater to acclimate to the water temperature for at least 15-30 minutes before setting the desired temperature.

Important Installation Notes: The heating rod must be completely immersed in water during operation. For optimal performance, the heating rod should work with a water pump that circulates the aquarium water.
Operating Instructions
- Monitor Current Temperature: The external LED display will show the real-time water temperature.
- Set Desired Temperature: Use the temperature adjustment buttons (up/down arrows) on the controller to set your desired temperature. The adjustable range is 63°F to 93°F, with 0.5°F increments.
- Heating Indicator: The "Heating" light on the controller panel indicates when the heater is actively heating the water. Once the set temperature is reached, the heater will enter a constant temperature state, and the light may turn off or dim.
- PID Control: The intelligent PID temperature control system will automatically activate the heater when the water temperature drops 0.6°F below the set point and maintain a constant temperature when it exceeds the set point by 0.6°F.
- Power Failure Memory: In case of a power outage, the heater will automatically restore the previous temperature settings once power is restored.

The external LED controller displays real-time temperature and power, with clear indicators for heating, out-of-water, and overtemperature conditions.

Diagram illustrating the intelligent PID temperature control, showing how the heater maintains a stable temperature around the set point.
Maintenance
- Regular Cleaning: Periodically clean the heating rod to prevent algae and mineral buildup, which can affect heating efficiency. Always unplug the heater and allow it to cool completely before removing it from the water for cleaning.
- Inspect Power Cord: Regularly check the power cord for any signs of damage, fraying, or kinks.
- Check Suction Cups: Ensure the suction cups are securely holding the heater in place. Replace them if they lose their grip.
- Avoid Abrasives: Do not use abrasive cleaners or solvents on the heater or controller, as this can damage the materials.
Troubleshooting
The intelligent controller provides error codes to help diagnose common issues:
| Error Code | Reason | Solution |
|---|---|---|
| E1 | Heater away from water surface (out of water protection). | Fully immerse the heating rod in water. The heater will resume operation automatically. |
| HH | Overtemperature protection (temperature exceeds 95°F). | Wait until the temperature drops below 95°F. The heater will resume operation automatically. Check for external heat sources or proper heater sizing. |
| LL | Low temperature protection (temperature is below 59°F). | Wait until the temperature rises above 59°F. The heater will resume operation automatically. Ensure the heater is adequately sized for your tank volume. |
| E2 | Protection against abnormal temperature. | Disconnect the heating rod from the power supply for five minutes, then plug it back in. If the fault persists, contact customer support. |
If you encounter any other issues not listed here, please refer to the support section.

Visual guide to error codes and their corresponding solutions for the fishkeeper aquarium heater.
Specifications
| Feature | Detail |
|---|---|
| Model Number | SUS-FK089-800W |
| Power | 800W |
| Applicable Tank Size | 85-220 Gallons |
| Temperature Accuracy | ±0.1°F |
| Control Range | 63°F - 93°F (17°C - 34°C) |
| Heater Rod Dimensions | 12.4 x 3.15 x 1.57 inches (31.5 x 8 x 4 cm) |
| Product Dimensions | 17.4 x 7.11 x 44.09 cm; 1.17 kg |
| Manufacturer | fishkeeper |

Detailed specifications for various wattage models, including the 800W heater.
Warranty Information
This fishkeeper aquarium heater comes with a standard manufacturer's warranty. Please retain your proof of purchase for any warranty claims. For specific warranty terms and conditions, refer to the product packaging or contact fishkeeper customer support.
Customer Support
If you have any questions, require technical assistance, or need to report an issue with your fishkeeper aquarium heater, please contact our customer support team. You can typically find contact information on the product packaging or through the retailer where you purchased the product.
For online purchases, refer to the seller's contact details on the platform.





