When I first started doing research to decide which kind of system I was going to use, I was attracted to the simplicity of DWC- but no one could fully explain why some buckets got the snot while others didn't.
I eventually built an RDWC system- and got the snot. I tried everything to get rid of it and nothing worked until I got a chiller and brought the nutrient water temps down below 68f. After that, I never had a problem with root rot again, EVEN WHEN I INTENTIONALLY ADDED WATER I KNEW HAD PATHOGENS IN IT.
Now I have multiple big tubs connected to a control bucket with a cooling coil and the recirc pump in it. The recirc pump feeds water into a manifold which then distributes the water to elbow fittings in the lids of all these tubs, where the water falls down to the waterline... waterfall style. This approach eliminated the air pump, lines and stones. It's rock solid reliable, no special snot killing sauce required- ever. I don't even do more than a cursory rinse between runs.
Therefore, based on extensive personal experience, I'd say that a big pond would work fine- as long as the water is kept in the dark, adequately oxygenated and that it's kept cool, below 68f, and below 65f would be even better. And yes, covering the roots to keep them in darkness is necessary and desirable.
As far as nutes go, water bottle brands will clean your wallet right out. Jacks is the standard recommendation, but any dry chemical nutrient system should do fine. I use Hydrogardens.com.
Good luck and let us know how things work out for you!