I have been using my locally grown sourdough starter for about a year
now and never get the fluid or foaming on top. I refresh once a week
at 100 % hydration, i.e. Every Saturday night I take 4 oz starter (by
weight not volume) and mix it with 4 oz water until dissolved and
then mix in 4 oz of all purpose flour. If I wait 2 weeks before
refreshing I will get separation. I bet the reason is the
carbohydrates are breaking down releasing more water and the proteins
break apart so not as much water is absorbed. I usually only bake on
the weekends so it would be smart to refresh Friday night but I
usually fall asleep. Instead I found that if I take 1 oz (heaping
tablespoon) of starter and mix it with 1 oz water and 1 oz flour and
leave it out overnight, the 3 oz of refreshed starter does a very nice job.
Lloyd