Tetra Goldfish Auto Heater 50W for up to 20L

Set of 3 heaters. New and unused, but have been stored at home for a long time.
As shown in the photos, this is a set of 3 heaters in total: one from Tetra and two from GEX.
Shipping is covered by the seller.
Below is a description of the Tetra heater as a representative example.

A 50W heater to maintain the appropriate water temperature for goldfish. With a safety cover, it is suitable for up to 20L.

- Brand: Tetra
- Model Name: Goldfish Auto Heater 50W
- Applicable Water Volume: Up to 20L
- Temperature Setting: 18℃
- Features: With safety cover
- Material: Plastic

Reference: Reason for purchasing new in the past and reason for selling now
Although I have fortunately never experienced it, there are rare cases where heaters malfunction, either staying on and causing the water temperature to rise, or conversely, not turning on and causing the water temperature to drop. To maintain water temperature even in the event of a heater malfunction, I used multiple low-output heaters. If one heater malfunctions and stays on continuously, the other heaters will detect the temperature and turn off, preventing the temperature from rising too high. Conversely, if one heater breaks and stops working, the other heaters will be on, preventing the temperature from dropping too low.
In addition, I kept spare new heaters at home in case of sudden failure, but since I decided to switch to a larger aquarium, I no longer have a use for them. I would be happy if someone could use them.