They’re unsuitable for saltwater or brackish aquariums. Submersible aquarium heaters can be fully submerged into an aquarium, so they’re generally more effective than immersible options.

【Comprehensive Protection Submersible Aquarium Heater】-- Our submersible aquarium heater have 2 intelligent protector to avoid damage to the product and its circuitry. ①Over max temp ...

HITOP 25W 50W 100W 200W 300W Adjustable Aquarium Heater, Submersible Fish Tank Heater Thermostat with Suction Cups (100W-grey) Haisen 7530 ratings ...