[thegrandpoohbah]

The rule of thumb is 5 watts per gallon so 150 watts is about right. That's what I would use. I've lost faith in the Jagers after a couple failed. My preference at the moment is the Fluval E series though they don't seem to come in a 150 watt model.

 

[thegrandpoohbah]

I've run my E-300 on a 45G and a 75G. Flow isn't a concern for me, I am running Rena XP3 canister filters.

 

[thegrandpoohbah]

Yup, people tend to go overkill on the wattage. Then if the heater gets stuck in the on position....cooked fish anyone?

100 watts is good for 20-40 gallons, so I wouldn't go more than that.

I used to think that too. Then I moved up north where it gets below -40C in the winter. I tried to use a 100W heater in a 26G tank, it only managed to get the temp up to around 72F (I aim for 78F in my tropical tanks).

And to the OP, I retract my recommendation of the Fluval E series heaters. Mine JUST crapped out last night after less than a year. It will now only adjust the temperature up and not down. I figured the temperature setting might cycle around again but no, it just maxes out at 93F and stays there.