Low Watt Heater?

[Cookielici0us]

I set up at 55 gallon tank today, but I forgot to buy a heater before sticking all my fish in there...
I know they like warm water and all, but what would happen if I used a 10 gallon heater in a 55 gallon?

My friend said the tank just wouldn't heat properly, so I was thinking DOES THE HEATER OVER WORK AND ELECTROCUTE ALL MY FISHES?

 

[Aquascaper]

The heater will either be on constantly/more frequently and just use more electricity OR it could overheat, breakdown and possibly crack allowing the element to come into contact with water and cause electrocution.

I would advise getting a new heater rated properly for your tank asap as a safeguard.