Can you use to big of a heater?

[Wildcat157]

I have a 150 watt ebo Jagger in a small 20 gallon tall I use for fry, or to occasionally separate fights before rehoming some cichlids. This is approximately 7 watts per gallon. If the heater is a reliable brand with thermostat is there any problem with using a big heater in small tank?

 

[1 2many]

No, no problem using that size heater. I use a 200 watt heater on a 20 gallon long without any issues.

 

[Wildcat157]

Ok. Good to know.

 

[TwoHedWlf]

I have a 150 watt ebo Jagger in a small 20 gallon tall I use for fry, or to occasionally separate fights before rehoming some cichlids. This is approximately 7 watts per gallon. If the heater is a reliable brand with thermostat is there any problem with using a big heater in small tank?

No, that's fine. For all realistic cases it is impossible to use too big of a heater.

Now, for the fun unrealistic cases

If you put a really giant industrial water heater in the tank, it might take take a minute to start heating the water and switch off. But by then built up so much heat internally that it will still heat and boil your fish before it cools back down.

 

[Wildcat157]

Lol.
That's hilarious.

 

[jjohnwm]

Well...there are a couple of reasons to perhaps re-think this. First off, one of the most common types of failure in an aquarium heater is having the thermostat stick in the "on" position. When this happens, the heater won't turn off, just keep on cookin'. Any given wattage of heater will be able to raise the tank temperature only so much, and that amount of increase will be much higher with a bigger heater, which increases the chances of killing your fish before you discover the problem.

Also, since a large heater heats the water more quickly, it will turn off faster...and then when the water cools, the heater clicks on again and then quickly off due to the speed of heating...and so on. Bear in mind that the heating element itself is either on or off, with no "in-between" operation. The thermostat will cycle on/off far more often than a tank that has a heater that is barely sufficient. The ideal situation would be a heater that stays on all the time and never cycles on/off, because the thermostat wouldn't be constantly clicking on/off and would last longer. Yes, eventually the heating element will burn out, but that tends to happen less often than stuck thermostats.

The bigger heater will definitely do the job, but should be monitored more closely.

 

[hey_wood1981]

The bigger heater will definitely do the job, but should be monitored more closely.

All solid advice. One other important thing to keep in mind is ambient temperature, and how many degrees you’re needing to raise your aquarium temp.

It’s been recommended to use a heater no larger than 150w. For larger tanks, use multiple 150w heaters. With heaters it’s not a matter of if the heater will malfunction, it’s when. More times than not it malfunctions and stays on.

The benefit of having multiple 150w heaters is if one malfunctions and is stuck on, it will take longer for your tank to reach dangerous temps. Another benefit is if one malfunctions and simply quits working, the other ones will keep the water temp from dropping quickly.

It’s not a bad idea to have an extra heater on hand either. You usually notice you need a new one at the worst time. That, and depending on where you’re at, shortages are a thing now thanks to Covid. Not to mention rising prices.

 

[duanes]

Well...there are a couple of reasons to perhaps re-think this. First off, one of the most common types of failure in an aquarium heater is having the thermostat stick in the "on" position. When this happens, the heater won't turn off, just keep on cookin'. Any given wattage of heater will be able to raise the tank temperature only so much, and that amount of increase will be much higher with a bigger heater, which increases the chances of killing your fish before you discover the problem.

Also, since a large heater heats the water more quickly, it will turn off faster...and then when the water cools, the heater clicks on again and then quickly off due to the speed of heating...and so on. Bear in mind that the heating element itself is either on or off, with no "in-between" operation. The thermostat will cycle on/off far more often than a tank that has a heater that is barely sufficient. The ideal situation would be a heater that stays on all the time and never cycles on/off, because the thermostat wouldn't be constantly clicking on/off and would last longer. Yes, eventually the heating element will burn out, but that tends to happen less often than stuck thermostats.

The bigger heater will definitely do the job, but should be monitored more closely.

I agree with this.
I have had a few of the large heaters fail in the "On" position, and cook the fish ( especially possible in small tanks).
Even had a large In-Line heater start to melt the PVC plumbing it was attached to.
I much prefer using 2 or even 3 smaller heaters per tank, where if one fails in the "On" position, the other two cycle off, and alone a less powerful heater does not have the capacity to overheat the tank, or........ if one less powerful heaters fails by shutting down, the other two are still able to pick up the slack.

 

[Wildcat157]

Thanks. Great advice for all.