Have you studied the process. I think you would be surprised. Not to be contradictory, but everything I’ve studied over the past year is different. I googled it and the first 3 sites said what keeps it from souring too much is due to submersion in lactic acid.
If you Google DE and ACV you'll find the top hits all say these are magical items that cure all ills. That doesn't mean that's true.
Yes, I have studied the process (I loooove Google Scholar). Water does not stop microorganisms from moving through it. Otherwise you would never ferment anything using the 3 inches of water method; you'd simply get no "good" bacteria getting into your ferment. Plus we'd have never had to come up with fridges if water was such a great barrier to bacteria. We'd just keep everything submerged in water.
Add to that that it needs stirring, completely negating any supposed barrier effect of the water.
Air locks on demi jons work because the passage is small and there is always movement upwards (the co2 may also play a part). Not simply because there is a barrier of water.
Souring is due to the lactic acid. This is produced by the "good" bacteria that you are trying to promote. These feed off sugars and alcohol. The "bad" bacteria, and yeasts, feed off sugars and in the case of yeasts produce alcohol. What prevents the bad stuff from growing is not the water, and not the lactic acid (although that is a contributing factor), it is the "good" bacteria chomping up all the food AND the waste products of the yeasts. The bad bacteria just can't keep up when they're actually making a food source for their competitors.
If you have a lot of water you've actually watered down the lactic acid, so any antibac qualities it has are reduced. Not just that, but some bacteria thrive better in slightly acid conditions as opposed to neutral (rare ones, but they do exist).
None of the fermented feeds I’ve seen for chicken feed shows 50:50. They all say it needs to be 1/3 or jar filled and a 1 in layer of water on top.
Then can I recommend TikiJane's article? It's a great cover all and I know I'm not the only one to have moved to her method.
https://tikktok.wordpress.com/2014/04/13/fermented-feed-faq/
Most brewers will tell you to bump the beer or wine if there is mold. Good way to get sick. It means the fermination has stuck and alcohol hasn’t killed off bateria aenobolically. Unless it’s Krausen, which is different
I would think ALL brewers would tell you to dump mouldy beer and wine. It tastes baaaaad
I highly rec the 50:50 method. It is way less messy and time consuming, and works just as well.
Though I can't say I agree with TikiJane's conclusions re chlorinated water. When I was letting the chlorine evaporate from my water I ended up with FF that had a good whiff of alcohol about it. I researched chlorine and found yeasts are more susceptible to chlorine than most bacteria, particularly good ol lactobacillus. So tap water might hurt the good bacteria a little, but it kicks yeasts hard. I ferment overnight, with tap water, in the 50:50 method using backwash, and it works great. It gets nice and bubbly, has a good sour smell to it, and my girls love it.