I have 2 of these plus an older different brand aquarium tank heater for a 100 gallon plastic trough for an outdoor pond. I got these as I had 2 of the other brand and 1 stopped working and had a pleka (wrong spelling) die from the cold and my turtle went into brumation. Since I have gotten 2 of these heaters, the water seems to stay warm enough for the turtle to stay out of brumation and the other fish alert. What I don’t like about them is I cant visibly see the dim blue light it claims to have to see they are on, but I can tell they are keeping water to set temp as the steam coming from the surface when it gets in the 40s so they are doing their job. Only been using for about a month, time will tell.