How many or what wattage of heaters do I need for a 300gallon?

[clare]

I suppose it depends on the temperature of the room the tank is in,the colder it gets the more heat required,we have all but one of our tanks in the same room and although each tank has heaters we keep the room at 76 so heaters only come on rarely.Alot cheaper.

 

[Booger]

I use (2) 400 watt heaters for my 300 in the garage. It gets down into the 40's at night and my tank stays at 80 no problem. Be mindful of your circuit as it's easy to blow a 15 amp circuit with a bunch of heaters.