Heater. How many watts?

[gwand]

I have a new 29 gallon tank 30LX12WX18H inch. How many watts should my heater have? Thanks.

 

[MaloK]

I always round that at 5 watts per gallons. So for your tank I would go with 150 Watts.

 

[Magnum Man]

I’ll add X 2, even if you just keep it in your supplies… it’s really not good for a tropical tank to go temperate for a couple weeks, while you get a replacement… so, most of mine are 300 to 500 watts ( for normal aquariums, and I have several spares )

And I look at it like this… it takes a certain amount of watts to heat your tanks volume, depending on the surrounding temperature… if you have a 100 watt heater it’ll run for so long, the 300 watt will run 1/3 of the time, so your electric use is the same… it won’t be any cheaper to run, with a half size heater, as the bigger one only runs half as much…

Often the bigger heaters have better controls, and may last longer…

I actually have a 300 watt heater in 2 - 10 gallon tanks, and those tanks are much more stable, than the 2 tanks with little heaters they make for small sized tanks…

 

[Back in the fold]

What @Magnum Man said is right on . A small heater will run almost continuously if the room is cold . My fishroom is cold in the winter . I just got a 125 watt Eheim for my 20 gallon that’s closest to the window and I rarely see it on but the aquarium stays 80 degrees while the room temperature is 68 .

 

[Archerfish]

It depends on the temperature range of the fish you desire to keep and the temperature differential between ambient room temp and your desired tank temperature. For example, no heater is needed if you want to keep a species tank of white clouds unless your fish room is an icebox. Calculate the differential and then decide the heater (s) size. Watts per gallon is useless for selecting a heater or lighting unless you know the requirement.
Note: I edited the last sentence to say unless you know the requirement. Use heating watts per gallon once you know the temperature required. Didn't mean to confuse!

 

[MaloK]

I try to balance heater power and water quantity to have ideally 1-1.5 Fahrenheit rise per hour maximum.

So if the tank drops 10 degrees during a power outage it should take around 7-10 hours to bring back the tank to temperature.

If the heating is too overpowered and the tank heat back up too fast, It causes stress to the inhabitants.

A 300 watt in a 10 gallons would heat 5 times faster, from 5-7.5 degrees per hour. That's too fast for me.

There's also a greater risk to cook everything in case of failure.

Slow and steady, with a 10 degrees difference between room and tank. Your heater should be on from less than a quarter to a third of the time. From 15 to 20 minutes per hour.

For all it worth, It's the way that it was shown to me 45 years ago by a Guru and believe he was right on.

 

[ghyti]

An old rule of thumb says Watts = 3 to 5 times Gallons. A 300 - 500 watt heater is fine in a 29 gallon until it sticks on one night and cooks your fish. A lot of people use two small heaters instead of one big one to avoid this problem.

 

[MaloK]

Agree, 5 watt per gallons is basically the maximum used in cool rooms.