osymandius, actually low O2 may become a problem sooner than later "since you are"sheltered by trees which equates to windblock and more natural organic matter from the trees. Being sheltered from the sun will lower oxygen levels faster than full sun with out the trees.Jeff is correct about running a single tube in your situation 300 ft is not a problem.(somewhere between 3000-5000 ft of tube we would reconsider)You would only need a small system that would give you 1-2 turns per day, Im not sure what the dc to ac conversion would cost but you can probably can do an entire system with the trunk line for less than conversion and or solar would cost plus youll still need most of the same basic system . If your KW cost is in the 12 cent range figure $19.00 per month to run 24/7, I also sent you a PM