How many heaters should I use?

Hi, I recently set up a 125 gallon which I transfered my oscar and his filter over to. I currently have one aquatop 500watt heater in the tank which is rated up to 150 gallons. I also have a couple thermometers in the tank to check the temp and make sure the heater is working. I have a second of the same heater and was curious if I should run two heaters in the tank. so far the heater is preforming quite well with no changes in temp acording to the heater thermometer and stand alone thermometer. If yes should I stick the other identical heater in there or run a smaller one along side the one in there now? Thank you for all of your help im open to everyones opinion.

 

Hi, I recently set up a 125 gallon which I transfered my oscar and his filter over to. I currently have one aquatop 500watt heater in the tank which is rated up to 150 gallons. I also have a couple thermometers in the tank to check the temp and make sure the heater is working. I have a second of the same heater and was curious if I should run two heaters in the tank. so far the heater is preforming quite well with no changes in temp acording to the heater thermometer and stand alone thermometer. If yes should I stick the other identical heater in there or run a smaller one along side the one in there now? Thank you for all of your help im open to everyones opinion.

I personally like to run 2 heaters in case one malfunctions. Plus it helps distribute the heat better.

 

I personally like to run 2 heaters in case one malfunctions. Plus it helps distribute the heat better.

is the second identical heater too much?

 

is the second identical heater too much?

In my 125g I'm running 2 300W heaters, 2 500W heaters may be overkill, but as long as they work they should keep each other shut off when at the right temp

 

Also have 2 heaters in each of my tanks. I think it helps reduce variations. And prevents accidents if one of them stops working.

 

In my 125g I'm running 2 300W heaters, 2 500W heaters may be overkill, but as long as they work they should keep each other shut off when at the right temp

As long as you dont think it would hurt the tank for some reason im fine being overkill i already have a second one. Im able to return it so if you think I should return that one and get a smaller 2nd one that would work too.

Also have 2 heaters in each of my tanks. I think it helps reduce variations. And prevents accidents if one of them stops working.

Do youthink 2 500watt heaters would harm the tank or should I return one and get a smaller one to go along side my 500

 

The only risk is that if one heater gets stuck in the on position the tank will overheat more quickly than with lower wattage heaters. I remember there was a thread here some time ago where someone used a 500W heater for a 60 or 65 gallon tank, it stuck on and killed all his discus before he noticed the fault. Obviously not quite such a big risk in a 125 and unlikely that both would stick at the same time.

I have 2 x300W in my approximately 150 gallon tank and 3 x 200 in my biggest tank (about 220 gallons). In a smaller tank (about 63 gallons) I have one x 200 and one x 75. I agree that for tanks over 50 or 60 gallons it’s best to have two heaters.

 

The only risk is that if one heater gets stuck in the on position the tank will overheat more quickly than with lower wattage heaters. I remember there was a thread here some time ago where someone used a 500W heater for a 60 or 65 gallon tank, it stuck on and killed all his discus before he noticed the fault. Obviously not quite such a big risk in a 125 and unlikely that both would stick at the same time.

I have 2 x300W in my approximately 150 gallon tank and 3 x 200 in my biggest tank (about 220 gallons). In a smaller tank (about 63 gallons) I have one x 200 and one x 75. I agree that for tanks over 50 or 60 gallons it’s best to have two heaters.

True. Would you recomend just getting a smaller heater to acompany the 500?

 

True. Would you recomend just getting a smaller heater to acompany the 500?

I am not sure what would be the best combination of heaters, but a smaller one with the 500 I am sure would work well, assuming you have good water circulation. It does also depend on your room temperature and the temperature you want to keep your tank at.

 

I am not sure what would be the best combination of heaters, but a smaller one with the 500 I am sure would work well, assuming you have good water circulation. It does also depend on your room temperature and the temperature you want to keep your tank at.

thanks for the help!

 

If you want to run two heaters fair enough.

I've been experimenting with heaters for over 50 years and overall I find it much less trouble managing with one.

For my situation in a heated house with a 120 gallon tank it's not a problem if my single 300W heater sticks on or stops heating because the temperature will not change enough to harm the fish before I notice. I have a stick on Fluval EDGE Digital Aquarium Thermometer which is very small and discrete but easy to read at a glance. The fish will also behave differently if they are uncomfortable.

Two heaters are double the trouble. Or worse.

Just ensure you have a spare.

 

No matter which brand of heater you purchase, sooner or later it will fail. It is not a matter of if, but when. There are two possible failure modes.

One is for the heater to fail in the on mode. That means that the heater will continue to heat the tank until you discover the problem and unplug it. If you are using a heater that is larger than required for the tank, you can heat the tank to the point that the fish will die due to lack of oxygen.

The second is for the heater to fail in the off mode. In that case the heater will no longer heat and the tank temperature will drop until it matches the ambient room temperature. If the room temperature is only a few degrees below the tank temperature, that might not be a significant issue. I have a couple of aquariums in my basement where the temperature can drop to 58-60 F in the winter, well below the 78 F temperature of my tanks. If the heater failed, the fish are likely to get sick or even die.

Thus, I recommending using two heaters each sized slightly below the requirement for the tank. The normal recommendation is 5 watts per gallon, but that only applies if the tank temperature is less than 5 degrees C (9 degrees F) above the lowest room temperature. If your room temperature is lower, as is the case in my basement in winter, larger heater is required.

So while a single 500 watt heater might be sufficient for your tank, having two 300 watt heaters would also be an option. Since you already have a second 500 watt heater, I would suggest using that in the tank as well. Set the temperature setpoint on the second heater just slightly below the setpoint on the 1st heater so that only one heater is normally functioning unless the temperature drops below normal.

Be sure both heaters are located in separate areas of the tank and in areas of high water flow. A 500 watt heater can get rather warm, so you want the heat to be carried away as rapidly as possible.

 

No matter which brand of heater you purchase, sooner or later it will fail. It is not a matter of if, but when. There are two possible failure modes.

One is for the heater to fail in the on mode. That means that the heater will continue to heat the tank until you discover the problem and unplug it. If you are using a heater that is larger than required for the tank, you can heat the tank to the point that the fish will die due to lack of oxygen.

The second is for the heater to fail in the off mode. In that case the heater will no longer heat and the tank temperature will drop until it matches the ambient room temperature. If the room temperature is only a few degrees below the tank temperature, that might not be a significant issue. I have a couple of aquariums in my basement where the temperature can drop to 58-60 F in the winter, well below the 78 F temperature of my tanks. If the heater failed, the fish are likely to get sick or even die.

Thus, I recommending using two heaters each sized slightly below the requirement for the tank. The normal recommendation is 5 watts per gallon, but that only applies if the tank temperature is less than 5 degrees C (9 degrees F) above the lowest room temperature. If your room temperature is lower, as is the case in my basement in winter, larger heater is required.

So while a single 500 watt heater might be sufficient for your tank, having two 300 watt heaters would also be an option. Since you already have a second 500 watt heater, I would suggest using that in the tank as well. Set the temperature setpoint on the second heater just slightly below the setpoint on the 1st heater so that only one heater is normally functioning unless the temperature drops below normal.

Be sure both heaters are located in separate areas of the tank and in areas of high water flow. A 500 watt heater can get rather warm, so you want the heat to be carried away as rapidly as possible.

A good way to avoid the malfunction is with something like an inkbird controller which will shut off the heaters if they overheat!

 

A good way to avoid the malfunction is with something like an inkbird controller which will shut off the heaters if they overheat!

I have never used an Inkbird controller for an aquarium as a second heater accomplishes a similar purpose. The only problem with the Inkbird is that if it fails in the off position and your tank is in a cold environment, the tank might get too cold. However, for a very large tank or a smaller one containing valuable specimins, the Inkbird would be a great recommendation.

BTW: I do have an Inkbird Sous Vide circulator that works wonderfully.

 

I would find out if you really need 500 watts first of all. How many degrees above room temp do you need? In my case with a tank half your size 100 watts is all I require and even on that one I installed a Ranco electronic controller to switch it on. The heater itself is set to a higher temp. The higher the amp draw of the heater the more likely the contacts could weld together.

 

If you want to run two heaters fair enough.

I've been experimenting with heaters for over 50 years and overall I find it much less trouble managing with one.

For my situation in a heated house it's not a problem if my single 300W heater sticks on or stops heating because the temperature will not change enough to harm the fish before I notice. I have a stick on Fluval EDGE Digital Aquarium Thermometer which is very small and discrete but easy to read at a glance. The fish will also behave differently if they are uncomfortable.

Two heaters are double the trouble. Or worse.

Just ensure you have a spare.

I’ve pretty much only used one heater at a time since I’ve started should I just stick with it and keep an eye on temp?

 

I've never had Inkbirds fail, but I have had heaters fail. I've used various brands. I've never had one fail in the on position thankfully. I've had them just stop working. The most common failure I've had is leaking water into the themometer. Another failure I had was when an aquen pro released a constant flow of bubbles into the aquarium from the bottom of the heater. It still heated ok, but I tossed it asap.

 

I use two 200w heaters for my 75g tank to keep it at 77 degrees. I also have a third 300w heater set to 74 degrees. So……the 300w heater just sits and is not being used. Should one or both 200w heaters fail and the water temp falls to 73, my 300w backup will kick in to save the day. I also use a Blue Line controller powering the two 200w heaters. It’s set to 79, so if my heaters should go crazy and stay on (over heating the tank to 79), the controller turns off the heaters. this way I’ve protected my tank from getting too hot or too cold. Yes…btw…..I do have a house auto generator for power outages.

 

You may also want to take a closer look at the circuit you are using, and what other loads it needs to handle. Running 1000w of heaters is a significant portion of the total load your circuit can take. You may not have the capacity for it anyway.

 

Good point for sure. Actually, though, w my setup, either the two 200w (400w total) …..or….. the one 300w unit is running at any given time bc of the BlueLine controller. There are a few low-draw devices like the two AC 110s, an air pump, and a few LEDs on the 15 AMP circuit.
But…..I like your thinking.

 

Good point for sure. Actually, though, w my setup, either the two 200w (400w total) …..or….. the one 300w unit is running at any given time bc of the BlueLine controller. There are a few low-draw devices like the two AC 110s, an air pump, and a few LEDs on the 15 AMP circuit.
But…..I like your thinking.

The way the thermostats are set on your heaters, you will NEVER be pulling 1000 watts. The duty cycle on the 300 W heater is effectively zero. It is possible that both of the 200 W heaters will operate at the same time, but unless one of those heaters fails, the 1000 watt heater won't operate. Thus, the most you might pull is 1 of the 200 watt heaters and the 300 w heater for a total of 500 W. The only time all three heaters might run simultaneously is if your furnace quits working in the middle of a blizzard and the house temperature plummets. But if that happens, you can place blankets over the aquarium to retain heat. It will take a 125 gallon aquarium quite a while to cool enough for the fish to be harmed. Hopefully, by then the furnace will be back online.

 

“….heaters will operate at the same time, but unless one of those heaters fails, the 1000 watt heater won't operate.”
I think you meant ….the 300w heater, not 1000w heater. Yes it (the 300w heater) just sits there inactive until such time that the water temp gets too low from the regular use 200w heaters failing somehow. Potentially the most that could operating power in a given moment is 500w. My tank is only a 75g, not a 125g.

 

inkbird controller helps , especially if you get a heater that has a history of being wonky. because it will turn the heater off once the target temp is reached