So between comments made here and the fact I can't get the heater that I bought to regulate right, I've decided to go ahead and buy a new heater (eventhough the one I have is less than a week old).
Anyway I'm pretty sure I am going to buy the Eheim Jager Thermostat Heater.
Currently our RES is in a 10 gallon aquarium. I know that long term he/she won't be there. When I do buy a new aquarium I am going to go ahead and buy what I hope will be the last (in other words big). My question is, can I buy a higher watt heater than what my 10 gallon aquarium needs? I mean if the wattage is higher but I set it at a certain temp, shouldn't the water stay at that temp whether I have 10 gallons or 100 gallons? If it is possible to buy a higher watt for now and use it on my 10 gallon, how do I estimate what size heater I would need? I mean if I have a 50 watt heater for 10 gallons now, does that mean I'd need 500 watts for 100 gallons (do they even make 500 watts)?

