The TetraTec heater has break and impact resistant glass tube, which ensures an optimal heat emission at the same time. At the adjusting knop the desired temperature is adjusted within the range of 19°C to 31°C in steps by 0,5°C. The star shaped structured heating element from chrom-nickel-wire provides for an even heat distribution. A control light displays, when the heater operates. The heater can be operated also fully submerged. For use in tropical and marine aquaria.