Terrible advice Tuesdays (T.A.Tues): The Zero Heat Return Pump

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 9.5 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.

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Comments for this article (14)

  • RGibson says:

    Can you tell me were to fine a Matted Filefish

  • Laurie says:

    Hi Mark,
    I wonder could you please advise, is it worth installing a refugium in a 28 gallon tank. my thoughts go along the lines of installing one in my garage and piping the necessary piping though the wall. My tank personality is one of a tank dabbler, but one day hope to have enough knowledge to reach the dizzy heights of a reef enthusiast.
    love your videos keep up the good work.
    Laurie (U.K)

  • Eddie says:


    What pump do you suggest for a UV?
    Water Blaster HY-3000w Water Pump
    Diablo DC 3500 Variable Speed Water Pump
    or ?


  • Eddie…I don’t use or recommend UV so I’d leave it off. And the flow rate for a UV sterilizer is very particular to its size. You have to make sure you get the flow rate correct or else the UV’s effectiveness is reduced.

  • Dan Gappa says:

    Off topic question… Does running a UV and carbon dosing at the same time conflict with one another? I was thinking and it just seemed to be not right… 120 gallon reef tank three months old, reef enthusiast

  • Dan…I covered the topic of UV and carbon dosing in the Midday Monday Q&A session a couple of weeks back. You’ll want to pick one or the other, but not both

  • timothy dufrene says:

    Mark, I had a Reeflo Blowhole 1450 external and changed to the DC powered Diablo 3500 internal. Just the opposite happened for me. A drop of 2 degrees in temp. I love this Diablo pump and much more room in my cabinet now. Also thanks for coming to our meet in “”Louisiana”” at Coral Fever. I didn’t get to see you speak because I was serving the boiled strip all day but I heard it was very good.
    P.S. sorry about the spelling thing!!
    Just having fun, Tim

  • Mark S says:

    I was away once for long weekend and the water level in my sump got too low. Needless to say the the casing on the return pump melted down. These guys can give off a lot of heat.

  • Nate says:

    I live in Northern Utah and have LED’s. My heater works year round (less in the summer) so having my pump add heat to the tank isn’t a big deal. That way I can use the excess heat instead of putting it into the air. Great advice Mark, whether its good or bad for your tank you definite need to have that in mind.

  • Adam says:

    After reading the title of this TA Tuesday I was hoping to read that someone thought adding ice cubes to your tank would keep the temp down.

    Keep ’em coming!

  • Frank says:

    RGIBSON You can find the Matted Filefish At Blue Zoo and Foster/Smith Live Aquaria. F/S sometimes has pairs for sell. Blue Zoo can find you if none in stock. Both have healty fish.

  • Jimbo says:

    Its a simple qusetion anytime you add a pump to your systems sump it has to be cooled by the surounding water and it will disipate thru out the water hence raising ones water tempature how much you need to keep an eye on that and make adjustments as needed.

  • Jimbo says:

    Use of UV,s Mark is certainly correct on making sure one uses the right pump- flow rate with using them but also only the water that goes thru,s the UV is going to gain any benefit such as less algae and parasites etc. We don,t use them mainly for that reason alone. Make sure your using the Quarantine Method as Mark as also written much about. And water quality is so Important also. Happy Reefing!

  • John says:

    I use UV and say one thing it will make the water heat up also.
    As pumps I gone to DC pumps as they use less power and heat and can adjust the flow on some of them.
    The UV’s I had for years and had no problems. You need to do if you going to use one read the flow it call for from the company.
    All said it up to you. There are many thing out there. If what you have and doing is working then good do not change it. But if it something that may make things better for the tank try it after to read what it said how to use it.

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