Fluval P25 Submersible Aquarium Heater – 25W, Shatterproof & Fully Submersible, Preset 76-78°F for Freshwater & Saltwater Tanks up to 6 Gal, LED Indicator, Safe & Durable Nano Tank Heater

This thing works like a charm! Just plug and play. Ever since I put it in my Fishtank, my little beta fish are so happy and warm. It’s automatically controlled by the thermostat set at the factory. I was a little freaked out at first when I thought of the idea of buying something that was controlled automatically, but no boiled fish yet! They’re warm and cozy and happy. If you’re on the fence about buying this for your beta fish, look no further than this heater. Buy your little beta fish a blanket before they freeze to death. I’ve been using it for about three months now and it’s held up so far. It’s the perfect size to fit into a 3 gallon aquarium.

This is perfect for my 3 1/2 gallon beta tank! Keeps it the perfect temperature for him. His name is Gill.

Works perfect in the spec 3

I was watching TV when I heard loud gurgling noises from my 10 gallon aquarium. I assumed it was my filter but it was coming from the heater. Of course this was odd. Suddenly, the water around the heater was bubbling very aggressively and then started to shoot out water. It looked like Old Faithful, boiling water shooting out of my open top aquarium, drenching the floor. After being frozen in fear for 2 seconds, I instinctively yanked out the plug and the boiling stopped. There was this weird black powdery stuff all over the surface and it stunk like burned rubber. The worst was the SMOKE coming out of the water and I was worried it would trigger the fire alarm of my building. I looked into my tank and saw my 6 rasboras swimming on their sides, darting and panicking. My 20 cherry shrimp, along with all the baby shrimp were doing the same. I knew they were all as good as dead. There's no way they could survive an underwater nuke caused by Fluval. The heater had a small hole, which I assume got cracked due to poor construction. This caused the toxins to leak out. I can't think of anything I did to have caused this. My last water change was a few days before, the heater was completely submerged, and there were no sudden temperature changes. I read somewhere that heaters should be replaced every 3-5 years. I wish there was a warning when the time was up other than having a mass extinction in my aquarium.

Ran a little hotter than I’d like for a beta. Added a secondary thermostat and now it works like a charm.

I use these in my 1 gallon isolation tanks for my bettas and they heat the tanks perfectly. No major fluctuations. It stays above 80 but less than 87. I think it could also work for a 2 gallon

Worked well at first for my 3.5 gallon tank, consistently keeping the water at 78 degrees. Now, after 3 months, the red light never turns green and it's constantly heating the water to 81 degrees which is too high. Did it's job while I was learning the ins and outs of tank life, but now seems like a risk at that temp.

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