What size heater do I buy?

[Komodo]

I will be purchasing a 120 gallon tank tomorrow, what size heater do I buy?

Should I buy one big heater or two smaller ones?




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[saradomin]

When I emailed Eheim about the right size heater for my 125 gallon, they recommended the 250w, which is good for 106-159 gallons. The right size of heater will vary from each manufacturer.

 

[troyd75826]

My 250w fluval e series cannot keep temp above 77 (set at 79) in room temp at 69. I suggest at least 2-3 smaller heaters


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[saradomin]

My 250w fluval e series cannot keep temp above 77 (set at 79) in room temp at 69. I suggest at least 2-3 smaller heaters


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There is only a 200w or 300w in the E series, nothing in between. Those are rated for aquariums up to 65 gallons and 100 gallons.

 

[troyd75826]

My mistake, mine is an e200; but the point is, the tank is a 55 gal with lots of circulation and in a room that fluctuates between 68 at night and 72 during day, and it can't keep 79.5. Redundancy is good in case of failure of one.


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[jrc0528]

I second redundancy.... use 2-3 smaller heaters across the back of the tank.

* If any 1 heater fails in the ON state it will lack the power to "cook" your tank before you have a chance to notice. (assuming you check your temps whenever you feed)

* if any 1 heater fails to operate the remaining heater(s) will keep the tank from cooling too much while you frantically scramble to buy another heater.

I'd look for a couple heaters rated 75-100 G, you don't really want rated over 100G or my first point above is somewhat invalid.

 

[J.Mcpeak]

See above.

A few smaller ones.
In some cases it isn't possible to heat a tank with one heater.

1 watt per litre. More if it's in a colder climate 2 if it's particularly cold.

120 us gal=454litre
120 imp gal=545litre
What's a Canadian gallon?

A pair of 250w-300w, some fish like it warmer so you may need more.

If the air temperature is considerably different you will need more energy to heat the water to the same temperature.

 

[dalto]

In order to select the appropriate size heater you need to understand how much you will need to heat. So consider the lowest the room temperature will be and the highest you will need the tank temperature to be. The difference between those and the size and shape of the tank will help you select the correct heater.

 

[ScottsPets]

All companies list different specs for their heaters. I'm a big fan of using a heater more than capable of heating your volume of water and controlling that with an additional controller. This should save your heater from constantly having to be powered on as well as adding a second layer of protection to prevent the heater from sticking in the ON position.

 

[54seaweed]

I run 2 200 watt eheim heaters in my 90 , each heater is rated for 100g one on both sides of tank keeps a steady 80* temp

 

[saradomin]

Eheim also recommended two 150w heaters for my 125 gallon. I should get the two heaters instead of one 250w right?

 

[dalto]

Whenever you get two heaters I recommend using an external heater controller. Otherwise, variations in the thermostat can either cause one to do all the work or the heaters to be constantly turning on and off.

 

[jrc0528]

Excellent point Dalto...

I run my heater with a digital temperature controller available on eBay.. Be careful as many of them are in C, not F.

I set the heater itself to 80-81 and the controller to 76-77. If the controller relay sticks on the heaters will still kick off on their own before cooking everything.