Let me start by saying I've used the DOUBFIVSY Pond De-icer for an entire winter season in my backyard pond, and it's been... interesting. The floating design works as advertised - it keeps a nice hole in the ice for my koi fish to breathe. I particularly appreciate how my fish gather around it on cold days, almost like they're having a warm water party.
The thermostatic control is hit or miss. When it works, it's great - automatically turning on when temperatures drop below 41°F and shutting off above 91°F. But I've had moments where I questioned its reliability after reading some concerning reviews about overheating issues.
The anti-bite cord is a thoughtful feature for those with curious pets or wildlife. My dog hasn't tried chewing it (yet), but the protective tubing gives me peace of mind. The cast aluminum construction does heat up quickly, just be warned - the surface gets HOT during operation.
Now for the not-so-great parts: While mine hasn't malfunctioned (yet), multiple reports of melting housings and even fire hazards are seriously concerning. I've taken to checking mine multiple times a day after reading these accounts. Also, placement is crucial - you really need to get it in the water before freezing starts for optimal performance.
For smaller applications like my neighbor's horse trough (about 8 feet diameter), it seems to work perfectly fine according to them. But for larger ponds, your mileage may vary significantly based on the mixed reviews out there.
Would I recommend it? With serious caveats. If you decide to try this de-icer, please monitor it closely, especially in the beginning. And maybe keep a fire extinguisher handy - just in case those worst-case scenarios turn out to be more common than we'd like.