What wattage heater?

[mandi]

What wattage heater should I buy for my new 20-gallon long tank? (Planning on getting a submersible one, if that makes any difference.)

 

[FishDan]

A minimum of 75 watts, but a 100 watt is probably better. Or, for a 20 long you could go with two 75 watt heaters to help ensure stable temperature accross the tank.

\Dan