Fluval M50 Submersible Heater 50 W, up to 15 US Gal / 50 L

A compact submersible heater sized for nano and small aquariums up to 15 US gallons, where a full-size 300W heater would be overkill and harder to hide. Fully submersible design and a straightforward mechanical dial make it a simple, reliable option for smaller freshwater setups that just need steady, unfussy heating.