Question as for h²o as mass

So I'll be building a new and improved greenhouse. I want to incorporate a rmh into my design alonld with earthbags. OK simple as I can put this. I want to use a normal rmh design but with 12" piping...I'll run this through an insulated aboveground cistrin with no less than 5000 gallons h²o. I will in turn pump this heated h²o into active liquid to air heat exchangers to heat the greenhouse. Has this been done? I realize I can't use stove pipe. I'll be using 12" .120" pipe with welds as needed and heat transfer fins. The mass tank will be a zero psi and vented to outdoor atmosphere...I'm not gonna attempt a pressurized system.. This will need to heat a rather large greenhouse until November in Craig co.....my rough GH dimensions will be 40'l x 30'w x 16'h at ridge line and 8' at north and south walls. So roughly overestimate of 19,200³ft to heat. And keep inside temp at no less than 50f.
Further greenhouse design will include earthbag exterior walls 4' tall and I'll be using clear polycarbinate for the roof and opaic poly carb for the remaining exterior wall space.
Thanks in advance

I haven't heard of exactly that being done, but there is one person who has built a 6" RMH which heats a fish tank in a greenhouse. He has brick channels under the water container, and as it is a modest system he just has a plastic liner to hold the water.
You would obviously need a stronger vessel - what are you planning to use? How will you seal around the 12" duct where it enters the tank? What tank dimensions do you anticipate? Where will the tank be located, and will you have planting area on top of it?
In principle it sounds like a viable plan. 12" is a very large system, and you will likely need to use top-shelf materials to stand up to the intense heat in the combustion core. Have you researched the "Rocket Stoves in Greenhouses" thread in this forum?
https://permies.com/t/19178/rocket-stoves/Rocket-stoves-Greenhouses-forum-topic

If you're in Colorado, which I believe is a sunny region, and you only want to heat your greenhouse till November, passive solar should be very effective, and much simpler and more foolproof and require less maintenance and feeding than this idea.