Heating Your Tank

[Kimbobble]

Hey guys, just wondering, I have a 65l tank, what wattage do I need for heating it? I kinda googled and it said 150 watts but i need a second opinion cheers

 

[StevenF]

It depends on how much heat you need.  For your tank a 50W heater might be sufficient.  It all depends the difference between the room temperature and the aquarium temperature.  Based on what I have seen 5C above the room temp would require a 50W heater.  A 15C temp difference would require 150W (http/freshaquarium.about.com/od/heating/a/heatersizeguide.htm). But these are just estimates.  The needed heat may be higher or lower depending on the tank (glass / acrylic), the sand (wood/metal, if  the  tank cover is used to reduce evaporation and A  the type and how bright light is.  
 
The only way to determine the exact size you need is to put a heater in the tank and measure the power (watt hours) it needs to maintain the desired temperature.  Ideally you want a heater that will keep it at temperature but will not have enough power to overheat the tank if the temperature control circuit fails.  A difficult balance to achieve.  
 
When I got my used aquarium it came with a heater.  I have found that it is has about double the power I need.