My starter is about the thickness of pancake batter. It is full of bubbles but not foamy. Occasionally it goes two weeks without a feeding, but it doubles again in twelve hours.
Taste & flavour
Take starter out of fridge and weigh it. Stir in half that weight in well water. Then add the same amount by weight in hard white bread flour. Stir until all is moistened and keep at room temp until doubled.