The EHEIM ThermoPreset aquarium heater allows you to maintain the aquarium water at a constant temperature without needing to adjust it. ThermoPreset is a heater for both freshwater and marine aquariums, pre-set to 25 °C to keep the water at a stable temperature. Very durable and featuring a sleek, minimalist design, it is barely visible in the aquarium thanks to its compact size. Available in 4 power levels, it is suitable for aquariums ranging from 25 L to 400 L.

Design & Construction

The heater has a slim, unobtrusive form: the body is 28.2 mm in diameter and its length (height) for the 150 W model is about 223.5 mm.

It features a plastic protective cover around the heating element, which adds to the mechanical stability and helps protect against impact or breakage. This differentiates it from EHEIM’s Thermocontrol line (which has adjustable temperature). There is an LED indicator (control lamp) to show when heating is active.  Also built in is dry-run protection: if the heater is not properly submerged (or in other dry conditions), it has safety features to prevent damage / overheating.

It comes with suction cups for secure mounting to the aquarium glass.

Construction supports use in both freshwater and marine (salt) aquariums.

Technical Specifications

• Power: 150 W at 50 Hz.

• Temperature: preset / fixed at 25 °C (not adjustable).

• Diameter of heater body: 28.2 mm.

• Length / Height: approx 223.5 mm.

• Appropriate aquarium volume: typically for aquariums of about 200 to 300 litres.

• Warranty: 3 years from the manufacturer.

Advantages of using Thermopreset 150 W Heater

1. Simplicity / Ease of Use: Because it’s preset, there’s no need to worry about setting the temperature. This reduces user error.

2. Good Stability & Safety: With electronic control the temperature is kept precise; dry-run protection helps avoid overheating if water level drops or it becomes partly exposed.

3. Discreet / Low Visual Impact: Slim body (2.82 cm) and moderate length make it less noticeable inside the tank, even in smaller aquaria.

4. Mechanical Protection: The plastic shielding helps avoid damage (e.g. from knocks, shifting décor, or handling) compared to heaters without such cover.

5. Versatility: Suitable for both freshwater and marine/aquatic setups.

Limitations 

• Since the temperature is fixed at 25 °C, you cannot set it lower or higher. If your fish or aquatic species need a different temperature (say 24 °C, 27 °C, or seasonal fluctuations), this heater won’t allow adjustment.

• For very large tanks, or where ambient room temperature is low, 150 W may struggle to maintain 25 °C, especially if insulation is poor or there’s heat loss.

• Even though there is dry-run protection, it’s important to make sure the heater remains properly submerged at all times during operation to avoid risks.

• The length (approx 22-23 cm) means it may still be somewhat visible or awkward to place in very small or narrow tanks.

• As with all electrical aquarium equipment, care must be taken when installing, maintaining, and cleaning, to avoid damage or safety issues.