@kevin The carrots in that jar were dry-salted, it's usually enough to just-cover them. Problem in this particular case may have been more than one thing. I may have overfilled the jar? When i do some liquid spurts out and it sometimes appears like there's less cover (carrots also expand in the jar, get pushed up and out of the liquid sometimes when fermentation starts) and i imagine that this paired with air coming in may have caused it?
@rek Interesting--I haven't experimented with dry-salting. Regarding the (assumedly) gas forming and pushing your carrots/liquid up, have you considered weights of some variety? We've got some glass disks that fit nicely in a wide-mouth mason jar but I've also seen glass marbles used. With our miso, we generally use a bag of grain or water which has the added benefit of reducing available oxygen by minimizing head-space.