How big does a heater need to be?

Originally posted by slipknottin
The point of using two heaters is that the temp change would happen much slower.

...

I am sure a "half heater" can still cook your fish while you're at work for 8-10 hours.

A good experiment would be to crank one of your "half heaters" and time how long it takes to overheat the tank. I am sure it’s a lot less than 8 hours.

If that's the case then using two heaters would INCREASE your risk - doubling the possibility of a thermostat failing.

Gumby
 
I dont know, I have a 90 gallon tank with two 200 watt heaters.

The tank is at 80 degrees and the heaters have never shut off yet.

Room temp is around 65.
 
Originally posted by Gumby7
A good experiment would be to crank one of your "half heaters" and time how long it takes to overheat the tank. I am sure it’s a lot less than 8 hours.

If that's the case then using two heaters would INCREASE your risk - doubling the possibility of a thermostat failing.

The odds of the two failing on the same day seem kind of slim. The odds of this happening 10 minutes after you leave for work on that day seem slimmer. If two heaters need to be on half the time to do the trick, then one would need to be on all the time to do the same trick. If half your heating can cook your tank in a few hours then you can probably stand to use smaller heaters.

Its a precaution, and may not work every time in every tank. Your chances of being able to catch a blown thermostat are increased, not decreased. You have more time to notice the problem, not the same, not less. You may still not notice in time. Personally, I have 2 tanks each with 1 heater. Hasn't been an issue for me yet. Others have had trouble with wipeouts from bad heaters, it happens. Redundant underpowered setups are the normal workaround if this is something you're concerned about.

Just something to consider, your mileage may vary.
 
Not trying to be a knob but help me size my heater(s) then.

48g
room day temperature 72f
room night temperature 60f (possible less) (room is north facing with a wall of glass and setback thermostat).

I figure 200watts but give me your estimates.

Gumby
 
200 watts sounds pretty good to me. It seems like the "old" rule of thumb was 5w/gal but lately alot of magazine articles and online articles/forums say more like 2-3w/gal. Yours is below 4, so I think it's still just fine. I personally have 2 heaters on my tank, and like the "backup" idea. Remember that heaters don'e always stick "ON". They can also break in the "OFF" position, which will make even more sense to have another heater.
 
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