Heating? Do I have enough watts?

[Lynsey]

I have a 75 gallon long tank. I got two 125 watt Ebo-jager heaters. One for each end of the tank. The Ebo-jager box says that a 200 watt heater heats 60-90 gallons of water, so two 125 watt heaters should be enough right? The would act as one 250 watt right?

 

[ewok]

depending on the room temperature being somewhat warm, i would say yes. personally i lean towards slightly bigger and would probably do 2 x 200's .... the rule of thumb being 5 watts per gallon (375 watts)...... the best bet would be to watch them and make sure they don't run constantly, if they do, you might need more.

i hate being marginal or borderline on anything tho, and i haven't yet boiled fish as a result of a malfunction.

 

[wetmanNY]

www.skepticalaquarist.com: "An old-fashioned rule of thumb was, two watts to raise each gallon five degrees above the ambient room temperature." So 150 watts would raise 75 gallons five degrees above the room temperature.

A good thing about a big tank is that, once it's at the temp you want, an overnight chill in the room doesn't affect such a substantial volume of water much.

Maintaining a temperature takes fewer watts than raising a temperature.

 

[NJ Devils Fan]

No, that is not enough. Get 2 200 watt heaters instead.

 

[JSchmidt]

As suggested above, the wattage required really depends on what the maximum differential between tank and room temp will be. In my tanks at home, where the thermostat goes down to 60 degrees (or lower) for 8 hours, I need at least 5 or 6 watts of heater per gallon, even in my larger tanks (e.g., 75 gallons).

I have a few 200 watt heaters for those tanks, but I've had enough heaters fail (even good brands) that I'm shifting to using more heaters of lesser wattage for all my tanks. I'd rather deal with the unsightliness of 3 heaters than risk cooking my fish.

HTH,
Jim

 

[carpguy]

Originally posted by NJ Devils Fan
No, that is not enough.

Truth is we have no idea whether or not thats enough. If we want to get from 68 (room temp) to 78 (water temp) WetMan's formula calls for 300 watts (4 wpg), not terribly far from the 5 wpg rule of thumb. But Linsey's room could be 62 or 72, and the desired water temp may not be 78. WetMan's formula makes sense and can be tailored to specific situations.

It never hurts to have a little extra capacity, but part of the redundancy thing is not having too much power on hand.