what size heater

[Casper]

I can't remember the sizes for tanks.
is a 50 watt enough for a 20 gallon tank?

thanks

[Aquarius0015]

The rule I'm familiar with is 5w/g. It depends on your local climate, room temp, etc.

[slipknottin]

3 watts per gallon should be plenty. Assuming you only want your tank 5-10 degrees above ambient.

[Aquarius0015]

My parents keep a cold house and we have central AC. :)

[jeffro426]

If you keep your house at 75 degrees all the time, youll be fine with the 5 0watt. Personally i would go with a 75-100 watt heater...it will be on less and runs less chance of it getting stuck on.