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Results 1 to 10 of 10

Thread: Mutiple Heaters

  1. Default Mutiple Heaters

    0 Not allowed!
    On my 45, I have two heaters for redundancy purposes and I'm planning on dong the same for my 55. So instead of doing one 200 watt, I'm plan on getting two 150 watt heaters. Thoughts?

    Also, how many of you do the same thing?
    55g: Planted Tank: Firemouth, Blue Acara, Rainbow Cichlid, 15 Bloodfin Tetras, and 8 Panda Cories

    45g Planted Tank: 2 Koi Angelfish, 19 Rummy Nose Tetras, and 6 Green Cories

    20g Planted Tank: 8 Harlequin Rasboras, 4 Peppered Cories, and 8 Amano Shrimp

  2. #2


    0 Not allowed!
    I see no reason to waste money on under-wattage heaters. It costs about a dollar more to get the wattage that works for your tank. I would get one. It's always nice to have a back up tho but a good heater should last at least a few years.

  3. #3


    0 Not allowed!
    I use two on larger tanks but IMO you should not reduce the wattage of the ones you use. This will just make at least one of them work harder and not last as long. As an example, I have two 300 watt heaters on my 90g. You can rarely get both heaters to be exactly in sync, so only one is usually on.

    Liters to Gallons conversion calculator

    "Keeping fish for any period of time doesn't make you experienced if you're doing it wrong. What does, is acknowledging those mistakes and learning from them." ~Aeonflame
    your argument is invalid." ~Mommy1

  4. #4


    0 Not allowed!
    +1 to above. A second heater is a back up in case the first one fails, so it shouldn't hardly come on. If the first one fails, then IT has to carry the main load. So both heaters should be able to heat the tank on their own.
    20gal long planted community

  5. #5

    Join Date
    Feb 2010
    Ypsilanti, Michigan

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    0 Not allowed!
    You don't want to oversize heaters though, because heaters can fail and shut off but they can also fail and lock on. If that happens and the heater is powerful enough, it'll cook the tank.
    300 gallon mega tank: sailfin pleco, clown loaches, silver dollars, roseline sharks, congo tetras, new world cichlids
    125 gallon office tank: Africian cichlids, synodontis catfih
    75 gallon community tank: bolivian rams, black skirt tetras, dwarf neon rainbowfish, corys, harlequin rasboras, otos, bristlenose and bulldog plecos, assassin snails, various shrimp
    60 gallon goldfish tank: fancy goldfish

  6. #6


    0 Not allowed!
    i use two smaller watt ones that way if one sticks on it doesn't cook your fish

  7. #7


    0 Not allowed!
    Quote Originally Posted by sheamurai
    both heaters should be able to heat the tank on their own.
    Yup. And one more point. 150 watts are about $22 for a good heater so you have 2 x $22 = $44. A 300 watt runs about $26 so you have $44 compared to $26. And only need to use one wall plug.

  8. Default

    0 Not allowed!
    I use 2 for even heat distribution. Using 1 is also fine. I've had a heater lock on before, luckily no fish died but the temp was in the 80's.

  9. Default

    0 Not allowed!
    Quote Originally Posted by Gumshoe218
    On my 45, I have two heaters for redundancy purposes and I'm planning on dong the same for my 55. So instead of doing one 200 watt, I'm plan on getting two 150 watt heaters. Thoughts?
    For redundancy purposes, it makes perfect sense. (Of course, as someone correctly noted above, heaters have two failure modes: die completely or get stuck in "on" position. Your redundancy only protects from the former.)

    As long as all heaters are working, the specific wattage does not matter at all, as long as the combined wattage is sufficient. (You can even use a wild mix of completely different wattages.) Two 150 watt heaters will do exactly the same amount of work as one 300 watt heater, assuming their negative feedback loops are working well (i.e. they don't "stick" in on or off position).

    Of course, if one heater fails, you'll end up with only one 150 watt heater. How well it will perform its duties will depend on how much wattage you really need in your tank. If you really need a redundant system that can sustain itself for long time even after one failure, better opt for two heaters, each with adequate wattage to maintain the tank alone.

  10. Default

    0 Not allowed!
    If you go with 2 heaters, keep in mind that its almost impossible to set them both to exactly the same temperature. Thus, one will always turn on before the other.

    If both heaters are of adequate size for the tank, then the heater that turns on first will be the primary heater for the tank. The secondary heater will never turn on and will be used only in event of a failure of the primary heater. The primary heater will do all the work.

    If both heaters are of insufficient wattage to maintain the set temperature, then one of the heaters will turn on and the temperature will continue to drop until the the secondary heater turns on. Depending on how far apart the heaters are set, the primary heater will remain on all the time with the secondary heater switching on and off to maintain the temperature. If they're set close enough, and their thermostat hystersis' are close, then you might see some sharing of the load, but this is unlikely.

    In the first situation, redundancy only happens if the primary heater fails open. If it fails closed, the tank overheats. In the second situation, there is no redundancy at all because if either heater fails, the temperature cant be maintained.

    There may be reasons to use two heaters, such as for distribution of heat, but redundancy isnt a good reason. You'd be better off with an over/under threshold alarming thermometer to let you know if the heater fails.

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