I have used both 50 and 25 watts in 5g's.The 50 I set at a lower temp then I would for a 25, just in case.
As long as its not a preset one like the tetra heaters. Mine never got above 74 even in a 1G and its a 50 watt heater.
I used to live in Alaska and when its -60 outside, it was like 60 or so in my ghetto apartment. I got most of my heaters via ebay - some are older models and they all worked pretty good but the only one to stay dead on the temp I set it at was the Marineland Neptune. I was kinda heartbroken it broke on the journey to NY :(
Last edited by Tikibirds; 01-07-2013 at 02:11 AM.