100w fish tank heater to heat a fermenter

[heshtek]

I've bought a 100w submersibile fish tank heater to keep my fermenter warm during the cold months when it will be sitting in my garage. I've decided to place the fermenter in a tub of water and heat the water surrounding the fermenter rather than directly placing the heater in the wort. If anybody has experience with this can you please tell me if a 100w heater should be enough to warm the fermenter during winter? Where I live we have several nights where the outside temp drops to 0 celsius. Also do I just set the fish tank heater to my desired fermentation temp or do I have to set it slightly above that? I'm asking because I presume the stick on thermometer will read the display the temp of the water that surrounds the fermenter rather than the temp of the wort itself.

Thanks in advance

 

[Ducatiboy stu]

Used to use one, but found 2 problems

1. The model I hade wouldnt go below 18*c

2. Needed to pull cap apart after EVERY brew as there where lots of places for infections.

Other than that it worked well