If you have ever touched an aquarium heater when it’s on, you’ll know not to do it again! Yet fish, especially sucker catfish and sucking barbs, have a habit of hanging on to heaters and as they don’t feel the heat, they can easily burn their undersides.
To prevent this, JBL aquarium heaters ( JBL ProTemp S 100 ) have a plastic basket that prevents the fish from coming into direct contact with the hot heater glass. And if the heater accidentally falls into the aquarium, the heater glass is protected from damage by the plastic protective basket.
Remember: always buy an aquarium heater WITH a protective basket.