I use tank heaters to keep my home brew warm while it's fermenting. It doesn't go in the brew, just in a tub of water around the fermenter. It worked fantastic for the roughly 8 gallons it was required for. The dial always seemed slightly off (had to turn it up 2F+ higher than what I actually saw with a digital thermometer) but it was consistent, I'm fine with that. It stopped working correctly after 10 months even though I treated it well and was always careful. I think the internal thermostat is broken, it turns on and off but even turned all the way up it's only heating to 65F which is not warm enough for my brew, I need it about 71F. I also purchased the 150Watt version from Hydor around the same time, that one is still working great but I'm concerned it will have the same fate as the 25W. I trying a competing brand with good reviews:Aqueon 06106 Pro Heaters Submersible Aquarium Heater, 100-Watt