Agree with the heating issue. During the day it stays pretty warm but nighttime will be a problem. The size of the mini split may be crucial. I'm guessing an 18k unit will be ok but it's just a guess. I have all kinds of crazy ideas like multiply poly sheets cut into panels i can pop in in Nov and pull out in April. Maybe sandwiched with bubble wrap for the roof with insulated curtains for the wall. I see Chinese GH's with a roll up cover that's 5-7 R value, but haven't had any luck finding ones not for giant greenhouses. The wood stove may be best bet. I get wood from a neighbor [his brother's a tree surgeon] and it might work as a supplemental heater to get through the winter. Then i have the reverse issue in summer. The pond itself may help regulate temps but it's probably not enough to make much difference.
