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Aquarium Heater Burn Out

edited December 2019 in General


After reading that some of you guys use aquarium heaters to keep a fermentation warm, I thought I'd give it a go. I'm using a 300W German-made titanium heater in a 250L fermenter which doesn't have any element control. I figured this would be more reliable by switching the heater on/off via a separate temp controller.

It worked great the first time. The second time, it has burnt out 3 days into the fermentation. I had it set to 30°C and the fermentation is largely finished (rum fermentation). When I looked at the heater tube, I can see that there is a 2-inch band of yeast which has "cooked" onto the titanium casing. Presumably that's the reason for the burn-out.

Has anyone had this issue before and how did you get around it please? Since the yeast will drop out of suspension as the fermentation dies down, it's surely inevitable that yeast will be exposed to the heater, because it's positioning is in the bottom third of the tank?


  • I had the same thing happen with an immersion heater because I was doing on grain fermentation. The solution is to have a second tank with a water heater and have a pump with an immersion coil circulating the water from the tank with the immersion heater. Immersion heaters try and heat up water by heating over the average temperature of the contact fluid. Is it efficient? Not really. Is there an alternative with ongrain ferments. Not that I know of.

  • Thanks @DonMateo. I've used the immersion coils on my smaller fermenters. They work well but it can be quite messy, so I'm going to have another try before I give up.

    Someone mentioned to me that they put their aquarium heater in the top third of the fermenter - not the bottom third as I did. I thought that seemed odd as heat rises, but then if I pump rum wash constantly from the bottom to the top, it would support top third placement of the heater. I think I'll get less of a yeast issue in the top third and the constant circulation might keep the yeast particles a bit more dispersed. Hopefully this will work. Failing that, I'm going to try a RIMS set up before I finally go to immersion coils.

  • I use a glass style one in the top third, never had an issue.

  • Thanks @grim - do you also have a constant recirculation of the wash - bottom to top - as otherwise top third placement of the heater probably won't get an even temp distribution?

  • We have mixers in our fermenters, but I don't remember every using them in long-fermenting rum wash where I would have been heating.

    Would imagine, for the most part, other than the very end of a long-running fermentation, that even minor co2 generation (bubbles) would keep the tank from becoming too stratified.

  • Ok thanks @grim. I guess I put my aquarium heater issue solely down to the bottom third placement in the tank

  • I have had success in using ULWD 240 devices at 120. This drops the power in half twice, or 1/4 the power, so I guess this makes them UUUWLD.. Put a blanket or other insulation on it and ensure you are pitching enough healthy yeast and you will soon be worrying about cooling....

  • I don’t remember exactly what I was using but it’s like 100-200 watts in 1000l to keep the temp up at the end of fermentation. It doesn’t take much. We are not talking about heating the tank, just keeping the temp from dropping too quickly.

  • I took a 9kw 3phase 2" TC heater (dernord from ali or ebay), wired the three elements in series and then ran at 120, it was perfect in 400L... calculating,, each loop is 19.2 ohms, so 57.6 ohms , which at 240v is 1000W, and at 120v which I used it at is 250W, which is right in line with @grim 's numbers

    I will also reiterate that a small circulation pump can speed fermentation 2-5x(and generate heat) if you pump from the very bottom of the cone to the top, or to midway with a racking arm aimed towards the top... the small 'tan homebrew pump' for $20 on amazon works great for this, and as a bonus can pump through a tube with the element in it(RIMS), or through a hx/chiller setup...

  • I use one of these and it works great for my rum washes that spike in temp.

    Thanks for the tip.


  • I do this too. Some things I learned: - Make sure the heater is vertical and not horizontal. This keeps it from scorching as much. - I try to put it as low as possible. - Over power it. I use 500w for 20g. - Aquarium heaters aren't meant for heavy usage. They won't deal well with constant heating. So the bigger you go helps reduce the load & extend the life. - I also prefer to waterbath my ferments. Put the heater in the waterbath. The waterbath also helps reduce the temp when the ferment it going full bore.

  • edited January 2020

    I gave up on aquarium heaters.

    These days I wrap soil heating cables on the outside of the fermenter and cover that with a layer of aluminium bubble wrap.

    I currently use a 24 m cable on a 160 litre fermenter. Ambient temp is less than 10 deg C and it is set to 20 deg C. It maintains it easily with just a simple Inkbird controller.


    232 x 800 - 36K
  • edited January 2020
    800 x 800 - 140K
  • That's pretty genius. Low temp at any point and it doesn't touch the wash. I am going to try that.

  • Yeah, I always thought the nice thing about it was exactly that. Even the metal tank all between it would further reduce any hot spots and create a larger heating surface area than the pad itself. Also, no contact with electric and water.

  • I always used cheap electric blankets with an insulating blanket round it.

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  • Try refrigeration door heater cable although that is self regulating so if you want a warm ferment it might not go high enough. Also used industrially as anti freeze on process pipelines.

    I use that and a thermowell into the wash and a Stc1000 (? ) temp controller. I sometimes use a heat and cool temp controller from somewhere like the keg king which is all prewired and use it to control both heating via tape above or cooling via fridge or coolroom depending on my ferment size. The tape works for me as my ferments are on the cool side.

  • Never once in 31 years of fermentations has heating been a consideration for me. Cooling. It’s always been about keeping it cool.

    I'm more like I am now than I was before.

  • I agree. While I do set up the heater I would be surprised if it ever came on whereas the cooling side regularly does. My fermenters were all setup that way for winter. It’s dead easy so why not. @Kapea you are in the tropics though so I would expect that.

  • @Kapea said: Never once in 31 years of fermentations has heating been a consideration for me. Cooling. It’s always been about keeping it cool.

    Ha!! I live in the UK ... (can't find a shivering emoji) :-)

    Thanks to everyone, this is a really helpful thread

  • IMHO - if you pitch enough viable yeast cells, and grow the starter correctly, you will only have to worry about cooling...

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