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  1. #1
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    Wattage for Water Heaters

    As many of you know heaters are rated in wattage - my question is what is the wattage per gallon that I need? How many watts would you for a 100 gallon system? 400 gallons? Thanks in advance!

  2. #2
    Aquaponics 101 Oliver's Avatar
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    The size of your fish tank heater in Watts is determined by the difference in the ambient temperature, the desired fish tank temperature and the surface area of the fish tank. All of these parameters are in direct proportion, meaning that a change in any of these is a direct change in the heater size requirement. It is also a function of the insulation value of the surface area, bottom and sides.

    To simplify, if you insulate the bottom and sides of the fish tank and cover it with clear plastic then the size of heater required is significantly reduced. If you set your fish tank on the ground or concrete without a bottom insulation layer, then the cold ground will draw out heat. The sides are exposed to the air which has less conductive value, so less heat will be lost from there. However, heat will be radiated from both the fish tank sides and out the top. A lot of heat will be lost through the aeration process, especially if the air being pumped into the fish tank has low humidity.

    Except for the aeration and top radiation losses, if you have good bottom and side insulation, the fish tank water should require little additional heat in order to maintain a constant temperature.

    Another source of heat loss is the grow beds. Again, bottom and side insulation will help reduce heat loss. If you have media filled grow beds and you flood and drain them, then the cold air being drawn into them will cool the media as well as cause some evaporative cooling, all of which will be transferred to the incoming water and then back to the fish tank.

    To answer your question, you can start with 3 to 5 Watts per fish tank gallon, but that would probably be a minimum. As can be seen from the above, there are a number of factors that will determine how much additional heat you will need to add to your system in order to keep the water temperature within the desired range.

    Oliver
    To measure is to know

  3. #3
    Members Apollo's Avatar
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    cormer.27 Welcome, I tried to add a line to this post and it duplicated it...please read next post.
    Last edited by Apollo; 10-19-2016 at 12:04 PM. Reason: Duplicated post

  4. #4
    Members Apollo's Avatar
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    cormer.27 Welcome, I live in the Phoenix area and have a 1000 gal system with a 500 watt heater. Which will keep my fish at or above 55 degrees when the weather gets down to 29 degrees.

    I'm border line on the size of the heater, I do have another 500 watt heater for a back up or if the weather gets colder. If you check out my system, "Pipe Siphon by Apollo" you'll see that it is mostly buried in the ground. To help with the heat loss on cold nights I have a spar cover & a tarp to cover the fish tank. I also change my fill & drain growth bed into a constant flow during the night, this helps a lot.

    Hope this helps...good luck, Apollo

    I HAVE NOT FAILED. I'VE JUST FOUND 10,000 WAYS THAT WON'T WORK. Thomas A Edison

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