Heater for 20 gallon high?

[airfix2]

what wattage of heater should i use for a 20 gallon high tank? i have a 20 gallon high aquarium which has a 125 watt heater, is this enough or should i get a 200 watt fluval m200 heater?

 

[carsonsgjs]

I’d have said 125 would be fine. Does depend what temperature you are aiming for and the temperature of the room, but you have plenty of wattage there to play with.