Originally Posted by Leigti
I have read so often that the water level needs to stay above the level of the green. I think it was because mold would grow on top if there wasn't a layer of water.
Leaving water on top keeps oxygen out, favouring the organisms you want. They only need a little air. I started by keeping the mix underwater and draining it off, but now I've got the hang of it I use one bucket with a couple of holes in the bottom. There is a second bucket beneath that, holding some ferment liquid in reserve should I empty the top bucket too much. You can start with submerged feed if you don't mind taking the time to drain it, but keeping it at serving consistency is simpler.
Once you have an active fermentation going, keeping the lid on the bucket will also help keep oxygen out. Fermentation eventually produces carbon dioxide, which is heavier than air and will stay in the bucket until you take the top off. It's pretty neat how a lively culture alters its surroundings to suit itself and keep competitors out.
I haven't seen anything mould-like since I switched to a drier mixture. The wet stuff generated either creamy gunk on top of the liquid, or a pale grey sprinkling on any feed that expanded above water level (this got stirred back in, having no particular smell). The sides of the bucket can get bits of dried feed stuck to them, but you can scrape this back down with your serving spoon.
I'm not convinced that you need ACV with the mother. I started with just rainwater and feed, have continued that way, and haven't needed to start fresh since I made the first mix a few months ago. I think ACV helps keep the pH down, but even "spiced non-brewed condiment" will do that.