How big does a heater need to be?

[superjohnny]

I have a 250w Ebo Jager for my 45 gallon. We keep my apt fairly warm... about 71*C or roughly 8*C under tank temp. I'm sure this is pleanty of heater (temps are stable), but is there any rule of thumb for how large of a heater to use?

[carpguy]

The really general rule of thumb is 5 watts per gallon. There is another, better, rule of thumb that has to do with how many watts you need to raise a given volume of water a given number of degrees. Except I can't think of it.

Having more than 1 heater is also recommended sometimes, so that its not as dangerous if one malfunctions.

My heater is only 3.3 watts per gallon, but it is hardly ever on. I suspect this has something to do with my plant lights. It seems to be more than enough.

[NJ Devils Fan]

The general rule is 5 watts per gallon, but it depends on how warm the room is. You should be fine. I also recommend 2 smaller heaters instead of one as stated to prevent your tank from boiling if thhe heater breaks and stays on w/out you knowing. Also, 2 heaters are a bit more efficient then one.

HTH

[JSchmidt]

Originally posted by superjohnny
I have a 250w Ebo Jager for my 45 gallon. We keep my apt fairly warm... about 71*C or roughly 8*C under tank temp. I'm sure this is pleanty of heater (temps are stable), but is there any rule of thumb for how large of a heater to use?

You keep your room at 71 C? That's almost 160 degrees Fahrenheit!!! At that rate, you don't need heaters at all... maybe you should invest in a chiller!

:D

Jim

[NJ Devils Fan]

Thats pretty funny, I didn't even catch that.

[superjohnny]

Originally posted by JSchmidt


You keep your room at 71 C? That's almost 160 degrees Fahrenheit!!! At that rate, you don't need heaters at all... maybe you should invest in a chiller!

:D

Jim

Yea, my wife and I are silicon based instead of carbon :D

I'm so used to working on my PC where I use the Celcius unit of measure. Anyway, thanks for the tips advice.

[Skippy]

160 degrees. hurm. that's almost warm enough for a discus tank.. right?

Oh no wait.. that's almost hot enough to COOK discus.

my bad :)

:D

[Gumby7]

Originally posted by carpguy
...

Having more than 1 heater is also recommended sometimes, so that its not as dangerous if one malfunctions.

...

No disrespect but I have some trouble accepting the validity of two "half size" heaters.

Assuming it is your lower night time room temperature which requires you to use a 250watt heater and not simple a giant tank (45g?). It would seem to me that a single "stuck on" 125watt heater would be sufficient to overheat the tank during the day when room temperatures are higher.

I guess if your room temperature is pretty steady and you sized your heater accurately then it would work.

Gumby

[slipknottin]

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

One 200 watt heater will bring up the water temp twice as fast as 1 100 watt heater.

[OCSupertones]

i have 500 watts in my 135, and i never have used my heater in my apartment this winter...the tank keeps it between 66-68 F...its great :)

[Gumby7]

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

[slipknottin]

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.

[carpguy]

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.

[Gumby7]

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

[Sumpin'fishy]

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.

[karfixer]

Having mulitple heaters will spread out the heat so that the tank is less likely to have hot/cold spots.