On Wed, 14 Oct 2015 12:07:22 -0500, Muggles wrote:

hmmm We don't have the space to do any more digging to bury stuff, but
we do have the metal circulation vent buried for the stove.

Have you looked into an outdoor patio heater for the green house,
placed next to the fish pond?

http://www.amazon.com/s?ie=UTF8&page=1&rh=i%3Aaps%2Ck%3Apropane%20patio% 20heater