found the same problem 300 W (4 year old) heater was sticked and killed some of mine discus fishes. i sended a complain to Rena , that heater does not do what has been promised.
The leaflet promised that overhaeting and sticking is prevented by a 500 micron silver coating.
will be kept updated on reaction of RENA.
positive or negative
Rena has a very good reputation on aquarium equipment and their 300w heaters are a good buy, good build quality and in most cases very good value for money. the heat element is sealed and in case of an accident would not be realised in the aquarium, there is also a lights that came up when the...