Charles Austen CB Series Aquarium Heaters
Charles Austen CB8300 Aquarium Heaters
Fully submersible thermostatic heaters from 50W to 300W for indoor freshwater and marine aquariums
Charles Austen CB8300 heaters are glass-bodied thermostatic aquarium heaters, not pond heaters. We have made that distinction explicit in the category name because a 300W aquarium heater is not a safe or realistic substitute for heating an outdoor pond.
Five wattages cover ordinary indoor tanks from 40 litres up to the published 600-800 litre range. Those figures assume normal indoor conditions. An open-top aquarium in a cold room, a high target temperature or strong evaporation can require a more conservative calculation.
A heater is small compared with the aquarium, but its position matters. Place it where filter circulation moves warmed water through the tank, protect it from impact and never energise it unless it is submerged as instructed.
CB8300 Size Guide
| Model | Rated power | Published aquarium range |
|---|---|---|
| CB8300 50W | 50 W | 40-60 litres |
| CB8300 100W | 100 W | 90-150 litres |
| CB8300 150W | 150 W | 150-300 litres |
| CB8300 200W | 200 W | 300-450 litres |
| CB8300 300W | 300 W | 600-800 litres |
These are manufacturer guide ranges for normal indoor use. The temperature difference between room and water is the crucial missing number.
Set and Check the Temperature Properly
Use a separate reliable aquarium thermometer; the heater scale is a setting guide, not a laboratory calibration. Adjust in small steps and allow the complete tank to stabilise before changing it again.
For valuable livestock, two smaller heaters can provide gentler distribution and some redundancy, but each installation must be safely controlled and monitored.
Safe Installation and Water Changes
Fix the heater where it remains fully submerged and receives steady flow. Isolate it before a water change and allow it to cool before exposure. A hot glass heater removed into air can crack.
Inspect the glass, cap, cable and suction cups regularly. Replace a damaged heater rather than attempting a repair.
Our advice: choose from tank volume and room-to-water temperature difference, then verify with an independent thermometer.
Related Heating and Installation Categories
Aquarium accessories · Aquarium air pumps · Water chillers · Water-testing equipment
Frequently Asked Questions
Are CB8300 heaters for outdoor ponds?
No. They are fully submersible thermostatic aquarium heaters for suitable indoor aquatic systems.
Which heater is listed for a 100 litre aquarium?
The 100W model covers the published 90-150 litre range under normal indoor conditions.
Which is the largest model?
CB8300 300W, listed for 600-800 litre aquariums under normal conditions.
Can I choose only from litres?
No. Room temperature, target water temperature, lid, flow and heat loss matter.
Do I need a separate thermometer?
Yes. Use an independent aquarium thermometer to verify the actual water temperature.
Should the heater sit beside the filter outlet?
Place it where circulation distributes heat evenly, while following the permitted mounting orientation.
Can it operate partly out of the water?
No. Maintain the required submersion and isolate it before lowering the water level.
How long should I wait after switching it off?
Follow the manual and allow the glass to cool before exposing or removing it.
Can I use two heaters?
Yes, where appropriate. Two correctly sized and spaced heaters can improve distribution and provide partial redundancy.
Why does the heater switch on and off?
Its thermostat cycles to maintain the set temperature. Very frequent or abnormal cycling can indicate poor position or sizing.
Can it be used in marine water?
Confirm the exact model guidance and keep all materials and electrical protection suitable for the intended aquarium.
What if condensation appears inside the glass?
Isolate the heater and replace it; moisture inside indicates a failure.
Can I bury it in substrate?
No. Keep it exposed to circulating water and mounted as instructed.
What electrical protection is needed?
Use a correctly protected aquarium supply with a drip loop and appropriate RCD protection.
Can you help choose a wattage?
Yes. Tell us the tank volume, room minimum, target water temperature and whether the tank is covered.
