Review on 🐠 Soyon 500W Aquarium Heater - Adjustable Temperature Fish Tank Heater for 80-100 Gallon Submersible Water Tanks by Josh Gerhardt

A used item was sent to me. Maybe it was used in a saltwater pool? There is sand and what looks like shellfish attached to the outside of the bottom of the heating element. Didn't see it as I looked up when I opened and placed it. My carp die the day I start using them. They moved away from the heater and began to die. The heating works. The water is 70 degrees but they are dying and when I inspected the heater I found the bottom was covered in sand and shells from someone's aquarium. My koi live outside, their pond has no substrate, it's bare and clean. very upset