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JBL ProTemp S (25-300w) (Safety Heater with Protective Basket) 1 review

by JBL
SKU J60421

safety heater-stat with protective basket


  • Plastic guard protects fish such as suckermouth catfish from direct heat.
  • Comes with dry run protection (turns off automatically when the water level drops or the heater is removed from the water)
  • Fully submersible and very robust 2 mm safety glass.
  • Direct temperature selection in °C.
  • Diameter of glass: 29 mm
  • Diameter on top: 36 mm
  • Diameter with cage: 33 mm
  • Diameter with cage + suction cup: 36 mm
  • Length incl. cage: 220 mm



When I touch the heating cable under water, it is only warm.

It is by all means correct that the JBL ProTemp S heating element only emits what is perceived to be pleasant warmth by the hand. The surrounding water causes the heat to be conducted away very quickly and passed on to the water. Therefore, the heating element is functioning properly. If it is taken out of the water, the glass immediately becomes very hot. The safety shut off is activated immediately. Nevertheless, the resulting heat must escape outside the water after the heating is switched off, which may cause the heater guard to become deformed, as there is no water to cool it. The safety thermoswitch in JBL ProTemp S heaters is by no means intended as an automatic control device which makes it unnecessary to pull the plug before a water change and, instead, is merely an additional safety precaution against accidents involving electricity. Due to its design, the heater may become very hot before the thermoswitch turns it off.

Is it possible that there is a series of JBL ProTemp S heaters with in/out intervals that are not adjusted properly?

According to technical specifications, our heaters have a control accuracy of +/- 05 °C. Taking measuring errors in temperature measurement for aquarium operation into account, the switching accuracy should be approx. 1 to max. 1.5 °C. If a heater has deviations of 5-7 °C, there is usually only one possible cause.

The heater is not adjusted properly, which can be determined by checking whether the heater has or has not a push button for readjusting (JBL has several different series). Otherwise it is defective. The heater is mounted in a spot that does not have sufficient flow of water.

Deformations have occurred on the protective baskets of the ProTemp S heater. What is the reason and what can I do about it ?

The protective baskets protect the ornamental fish against burns from the heating element.

If the heater is in operation it gives off heat to the surrounding water. With calcareous water scale (precipitation of calcium carbonate) can form where the glass meets the water and this reduces the thermal dissipation. An excessive formation of scale may cause heat accumulation which can lead to overheating and a deformation of the protective baskets.

With hard tap water a regular decalcification of the heating elements e.g. with JBL Clean A or JBL pH Minus is recommended.

Does the thermostatic switch in the JBL ProTemp S heater mean it is no longer necessary to disconnect the mains by pulling out the mains plug before a water change ?

The thermostatic switch in the JBL ProTemp S heater does not mean that it is no longer necessary to disconnect the mains by pulling out the mains plug before a water change. It is just an additional safety precaution against accidents with electricity. Due to its construction the heater can get very hot before the security switch switches off. This may cause a deformation of the protective basket.

Is the basket available as a spare part, or do I need to buy a new heater?

The protective baskets are available as individual parts. You need the following to fully replace the basket, e.g. for the ProTemp S 200 W:

1 x 6043100 – End part

1 x 6043200 – Short middle part

1 x 6043300 – Long middle part with a suction cup

1 x 6043400 – Upper part with 2 suction cups

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Filter Reviews:
Kian J.
Singapore Singapore

JBL ProTemp S 50

I was told there should be a lighting indicator when the heater is on. However I didn’t see any indicator and was unsure if the heater is working properly or not initially. The heater does feel a little warm upon touching it in water, hence I assume it should be working fine.

East Ocean Aquatic JBL ProTemp S 50 Review