Terrible advice Tuesdays (T.A.Tues): Pumping It Up Doesn’t Give Off Heat

Terrible advice Tuesdays (T.A.Tues): An internal return pump won’t add any heat to your saltwater tank.

The rest of the story: Internal return pumps are specifically designed to use the water they are submerged in to cool the pump. The heat created by the pump has to go somewhere!

Keep in mind different pumps will give off different degrees of heat. Pumps that are higher flow will use more watts of electricity and with the increased wattage comes increased heat produced by the pump. Also, just because the flow rates of two different pumps are the same, that doesn’t mean the pumps will consume the same amount of watts and produce the same amount of heat. Higher quality pumps will be more efficient at producing their flow rates and will produce less heat than high-wattage, less expensive pumps.

When I switched from a mag-drive 7 to a eheim 1262 on my old 90 gallon tank, my tank’s temperature dropped by two whole degrees. The increased price paid for the eheim was clearly worth it.

If you are going to be running an internal return pump, expect your tank’s temperature to rise. Exactly how much of a temperature rise depends on a multitude of factors including efficiency of the pump, other pumps in the system, temperature of the room, airflow around the tank, etc.

Finally, if you think you can avoid the heat issue by using an external return pump, think again. Poor quality external return pumps can heat up your tank’s water as well.

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Comments for this article (7)

  • Mark S says:

    One weekend when I was away my auto-top off failed and the water level in my sump got too low. The return pump, a mag-drive literally melted down.

  • Stuart says:

    Actually Mark if one lives in a northern climate and with now the colder temperatures especially in the winter the heat from the pump can be a good thing, your heater won’t have to work as hard!

  • Devin says:

    Man this is right on time!! I’m currently running a mag-drive 18 on my 180 gallon tank. I’m constantly having temp issues. When I checked last night my temp was around 80 degrees. I changed from halides to LED’s and it did go down some. I’m really trying not to have to purchase a chiller but am open to other options. Can you suggest another pump I could use to replace the Mag-drive 18 that will save some temp issues. I keep my house around 73-74 on average. I also have 2 reactor pumps in my sump as well.

    Seriously going crazy with the up and down of my temp as the lowest I’ve seen it was 77. Fish and coral are doing fine but after touching my water last night it was warm. I do get a little green hair algae on occasion and I’m wondering if my heat fluctuation is a part of that problem? Any help would be greatly appreciated. I don’t have much space/room for a chiller, so any suggestions on a small size that would fit my tank would be helpful as well.



  • Devin…check out the water blaster pumps. Also, you can try cooling fans before you go to a chiller. I always view a chiller as a last resort

  • David says:

    Wouldn’t an external pump with an exhaust fan solve most of these issues of heat retention?

  • Lyle Bradford says:

    don’t know if this will help but I just added a home made sump/tower wet/dry to my 55gal reef! All containers are plastic totes. drilled all of the top ones and stacked them like the original wet/dry towers! The water trickles/runs and falls over a foot + before it hits the sump and also have a side sump setting that up as a refugium! The longer fall time of the water before it hits the sump seems to cool it off some and the water is super oxygenated but not sending a lot of bubbles into tank! Just a thought! The very top container has filter pads both for dirt removal and chemical filtration! I buy the bulk sizes and cut them down to fit the container! The actual tower side stands over 2′ tall! Also running LEDS and two pumps on wave maker!

  • Tommy says:

    Heat tragedy…lesson learned. Don’t forget about the lights, too, as heat sources. Just had an Air Conditioner outage (not a full power outage) and forgot to turn off the lights. By the time I caught it the tank spiked to 90 degrees…the rest is costly history. I run T-5s and they really heat up the rig.

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