Heating requirements for a large tank

Bill Stock wrote:

....

The tank in question has a radius of 34" and a depth of 24", but I'll
likely keep the water at 18". This is roughly 200 gallons.

So roughly 6' across. Is this going to be outside ? This shape is much
different from a typical aquarium because there is more water surface
area compared to the volume.

If you have any airflow over the surface then that will carry away a
lot of heat. I don't think you will find a calculator that includes
that effect, or if it did it would be too hard to come up with the data
it needed to make an estimate. This is a wild card that can dominate
the heater requirements.


I tried a
couple of heater calculators on the web, one said 28W (LOL) and the
other said 700W. I was hoping for less, but I imagine the 700 is
close. Although the same calculator said I need 300-400 watts of
light for my 55 gallon. My poor Cardinals would need sun glasses.
I only want to raise the temp about 50 F on average.

A 50F difference is substantial, again much more than the typical
indoor application. Heater size goes up in proportion to the temp
difference. if you find a calculator, be sure that it includes this.

I can't offer much help figuring out the right heater for this
application, but it is clear that it is going to be something big. If
you can cover the top you will save a lot of electricity. If you can
cover the top and insulate around the bottom and sides then you might
get by with a simple 300W aquarium heater. An outdoor hot tub is not a
bad model for what you have described.

--

George