Unplug the heater and switch off the filter or pump. Remove the device from its pipes by unscrewing the lock nuts. Run the supplied brush through the water passage. Rinse the inside under the tap without wetting the housing or the cable. Refit it, restart the filter, then plug the heater back in once the air has been purged. Cleaning once a month stops deposits from skewing the reading.

Grey external heater with temperature display, black fittings at both ends and power cable

Contents of the external heater box: unit, spare pipe fittings, cleaning brush and cardboard sleeve

External heater mounted vertically on the outlet pipe of an external aquarium filter

Installation diagram: external filter under the aquarium and heater fitted on the pipe that runs back up to the tank

Box of the 300 W external heater, with the unit photographed on the front

Box of the 500 W external heater, with the unit photographed on the front

Contents of the JBL ProTemp External: heater with display, six pipe fittings, brush and box

JBL ProTemp External mounted vertically on an aquarium pipe, display and buttons on the front

Box of the JBL ProTemp External heater, with the unit photographed from the front

JBL ProTemp e or External heater, 300 or 500 W

Name: JBL ProTemp e or External heater, 300 or 500 W
Brand: JBL
SKU: J6042700
Availability: InStock

$54.80

$18.26 × 3 with no fees Klarna.

This external heater fits on the outlet pipe of an external filter or a pump: the water is warmed as it passes through, and nothing is left inside the tank. It adjusts from 20 to 35 °C, as the ProTemp e in 300 or 500 W, or as the ProTemp External in 500 W with key lock.

Ref. J6042700·Aquarium heater

Modèle : Protemp e

ProTemp e

ProTemp External

Puissance : 300 w

300 W

500 W

Customer support 7 days a week by email

Delivery within 2 to 15 business days

100 % secure payment

The summary

What it is: a 300 or 500 W heater that fits onto the outlet pipe of an external filter or a pump.
The setting: from 20 to 35 °C, with a display of the temperature of the water passing through it.
How to choose: the e300 heats 90 to 300 L, the e500 160 to 600 L, the External 10 to 600 L.
How it arrives: as a small parcel delivered to your door, with its pipe fittings and cleaning brush.

Heater to fit on the water circuit, outside the tank, for aquarium and aquaponics

This aquarium heater is not submerged in the water: it fits onto the outlet pipe of an external filter or a circulation pump, so the water is warmed as it returns to the tank. You no longer see a tube against the glass, and your fish cannot press against the heating element or knock it over. The ProTemp e is available in 300 W and 500 W, the ProTemp External in 500 W; all can be set between 20 and 35 °C and suit 12/16, 16/22 and 19/25 mm pipes thanks to the fittings supplied.

💧 Heat on the pipe

The principle is that of a flow-through heater, also called an inline heater. The water driven by the filter passes through the body of the unit, where a heating element transfers its heat to it, then it carries on to the tank along the rest of the pipe. A probe measures the temperature of the water passing through, and the electronics switch the heating off or back on to hold the setpoint. The display shows the actual temperature at all times. As the setpoint is saved, a power cut does not force you to set it again.

Pressure side

The heater is fitted on the pipe that returns water to the tank, never on the one that draws it in.

Upright

The unit should be mounted as close to vertical as possible, with water entering at the bottom and leaving at the top.

Below the water level

The body of the unit stays lower than the water surface of the tank, so that it never runs dry.

Near a socket

The cable forms a loop lower than the socket, so that no drop of water can reach it.

🌱 Heating an aquaponics tank

In aquaponics, temperature governs the comfort of the fish and the activity of the bacteria that convert ammonia into nitrate, and these bacteria slow down markedly when the water cools. An in-line heater suits these systems well, because the water is already circulating constantly between the fish tank, the filter and the grow beds. You fit it on the pump's outlet pipe, just after the pump and below the water level of the tank, before the pipe rises towards the grow beds. Warm-water species such as tilapia benefit from this steady heating, whereas for goldfish or carp it is often enough simply to protect the water from winter cold.

A pump out of the water when the tank has no external filter

If your system runs with a submersible pump at the bottom of a tank, the heater can be fitted on its outlet pipe. If you prefer to take the pump out of the water, the circulation pump, submersible or external is installed next to the tank and pushes the water through a pipe where the heater can be fitted. This way you group the pump and heater in one place, accessible without emptying the tank, which makes maintaining both easier.

Always lower than the tank's water surface

This heater must never be submerged in the water, but it should not sit higher than the surface of the tank it supplies either. If placed higher, it can drain when the pump stops, then run dry when it restarts. The safety cut-out then protects it from overheating, but your tank is no longer heated until you notice. Also switch the unit off whenever the water stops circulating, for example while cleaning the filter.

⚖️ 300 or 500 W

The ProTemp e300 heats 90 to 300 litres, i.e. an aquarium 80 to 120 cm long, while the e500 heats 160 to 600 litres, i.e. 100 to 150 cm long. Between 160 and 300 litres, both are suitable, and it is then the room that decides: a tank in a heated living room loses little heat, whereas a system set up in a garage, a cellar or an unheated greenhouse loses it much faster, so you are better off choosing the higher output. Count all the water that circulates in your volume, that of the fish tank as well as that of the filter and the grow beds. The display shows the temperature of the water as it passes through the heater: a suction-cup thermometer stuck on the opposite side from the water return confirms that the whole volume has reached the set temperature.

🔒 The ProTemp External

The ProTemp External follows the same principle with more complete equipment. Its heating element is made of ceramic, and its display shows both the water temperature and the set point, adjusted with three buttons. A button lock stops a child or a visitor from changing the setting, and an alarm flags any temperature deviation. Its 500 W output suits a tank of 10 to 600 litres. It comes with six swivel fittings for 12/16, 16/22 and 19/25 mm pipes, safety caps, a wall bracket and a cleaning brush. The wall bracket holds it upright against the cabinet or the wall, which makes installation on the pressure side easier.

🧽 Monthly maintenance

Over time, a deposit builds up inside the body of the unit, and it distorts the temperature reading if it gets thicker. Once a month, unplug the heater and the filter, disconnect the heater from its pipes, then run the supplied brush through the water passage before rinsing it under the tap. Make sure that no water gets into the housing or onto the cable, and wipe the outside with a dry cloth. When reassembling, start the filter first and let the air escape from the body, because a bubble left inside triggers the safety cut-out. Then plug the heater back in, and the display will return to the setting you had chosen.

Technical specifications

The essentials

Power: 300 or 500 WThe 500 W for a large volume or a cold room
Recommended volume: e300 90 to 300 L, e500 160 to 600 LTank, filter and grow beds included
ProTemp External volume: 10 to 600 L
Adjustment range: 20 to 35 °C
Display: Water temperature displayThe External also displays the set point
Feed: 220 to 240 V, 50 Hz

Installation

Location: Outlet pipe, pressure sideAfter an external filter or a circulation pump
Position: Vertical, upward flowA slight tilt is acceptable
Pipe fittings: 12/16, 16/22 and 19/25 mm
Fitting height: Below the tank surfaceIf placed higher, it may drain when the pump stops

Safety and warranty

Safety cut-off: Overheating and dry running
Power cut: Setpoint saved
Heating element: Glass on the ProTemp e, ceramic on the ExternalGlass must be handled without knocks
Key lock: On the ProTemp External

To budget for separately

Circulation: An external filter or a pumpWater must flow through the unit continuously
Pipe: Diameter 12/16, 16/22 or 19/25 mmThe one on your filter or your pump

8 further specifications are available in the detailed view.

In the box

1 external heater ProTemp e300, e500 or External, depending on the model chosen
Fittings for pipes of 12/16, 16/22 and 19/25 mm, 6 swivel fittings with the External
1 cleaning brush for the water passage
1 wall bracket and safety caps with the External
1 multilingual instruction leaflet, French included

Power ratings, volumes, adjustment ranges, fittings, safety features and warranty recorded from the JBL ProTemp e instruction manual on 08/10/2026, and from the JBL ProTemp External product page on 11/10/2026.

On the pipe, or submerged in the tank?

The three external heaters compared with the EHEIM thermocontrol submersible heater. The choice depends first of all on the flow in your circuit.

External or submersible? Three questions about your set-up, and the suitable heater is highlighted.

	Recommended ProTemp e300Your choice	ProTemp e500Your choice	JBL ProTemp e or External heaterYour choice	EHEIM thermocontrol aquarium heater, 50 to 300 WYour choice
Installation
On the outlet pipe, outside the tank	Yes	Yes	Yes	No
External filter or pump required	Yes	Yes	Yes	No
The power
Power	300 W	500 W	500 W	50 to 300 W
Recommended volume	90 to 300 L	160 to 600 L	10 to 600 L	25 to 1,000 L depending on the power
Comfort
Key lock	No	No	Yes	No
Heating element	Glass	Glass	Ceramic	Glass, submerged in the tank
Price	$54.80	$62.80	$98.27	$22.77

ProTemp e300Recommended

Installation

On the outlet pipe, outside the tankYes

External filter or pump requiredYes

The power

Power300 W

Recommended volume90 to 300 L

Comfort

Key lockNo

Heating elementGlass

ProTemp e500

Installation

On the outlet pipe, outside the tankYes

External filter or pump requiredYes

The power

Power500 W

Recommended volume160 to 600 L

Comfort

Key lockNo

Heating elementGlass

JBL ProTemp e or External heater

Installation

On the outlet pipe, outside the tankYes

External filter or pump requiredYes

The power

Power500 W

Recommended volume10 to 600 L

Comfort

Key lockYes

Heating elementCeramic

EHEIM thermocontrol aquarium heater, 50 to 300 W

Installation

On the outlet pipe, outside the tankNo

External filter or pump requiredNo

The power

Power50 to 300 W

Recommended volume25 to 1,000 L depending on the power

Comfort

Key lockNo

Heating elementGlass, submerged in the tank

Power outputs, volumes and installation methods recorded on 11/10/2026 from the JBL ProTemp e instruction manual, the JBL ProTemp External product page and the EHEIM thermocontrol product page. Compared product sheet: EHEIM thermocontrol aquarium heater, 50 to 300 W.

Estimate your
delivery time

The heater is sent in a small parcel with its fittings, delivered to your home by Colissimo or Chronopost, your choice at checkout. The exact cost is calculated in your basket according to the total weight of your order.

Frequently asked questions

8 questions

6 key questions, 8 in the detailed view

Do I need an external filter to use it?

With an external filter: you cut the filter's outlet pipe, insert the heater between the two pieces, and the filtered water is warmed as it travels back up to the tank.

Without an external filter: a circulation pump does the same job, whether it is submerged in a tank or installed out of the water, provided that it pushes the water into a 12/16, 16/22 or 19/25 mm pipe and that the heater stays lower than the surface of the tank.

What power should I choose for my water volume?

The choice is based on the total volume in circulation, then on the room where the circuit is located.

Total volume	Heated room	Cold room or greenhouse
90 to 160 L	300 W	300 W
160 to 300 L	300 W	500 W
300 to 600 L	500 W	500 W

What is the difference between the ProTemp e500 and the ProTemp External?

	e500	External
Volume	160 to 600 L	10 to 600 L
Heating element	Glass	Ceramic
Button lock	No	Yes
Wall bracket	No	Yes

What do the codes shown on the ProTemp e display mean?

E-1: the water is at least 1 °C warmer than the set temperature, and the code clears by itself as it cools.
E-2: the unit is short of water or contains an air bubble, and the remedy is to stand it upright with sufficient flow.
E-3: the electronics are faulty, and the repair is a job for a professional.
E-8: the internal temperature exceeds 93 °C, owing to insufficient flow or a clogged water channel, which can be cleaned with a brush.

Can it be fitted horizontally?

How to clean it?

Unplug the heater and switch off the filter or pump.
Remove the device from its pipes by unscrewing the lock nuts.
Run the supplied brush through the water passage.
Rinse the inside under the tap without wetting the housing or the cable.
Refit it, restart the filter, then plug the heater back in once the air has been purged.

Cleaning once a month stops deposits from skewing the reading.

Can it heat a 1,000-litre IBC tank?

How long is the warranty?

Let us talk about your project

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JBL ProTemp e or External heater, 300 or 500 W

The summary