After finally managing to cultivate a starter able to produce successful loaves, I've been storing it in the fridge and feeding it once a week by discarding half and adding equal weights of (white) flour and water.  I noticed that the starter was becoming thicker and it dawned on me that I've been pouring away the thin layer of hooch that accumulates on top, without adding extra water to compensate.

What's the correct way of dealing with this?  Should I be weighing the hooch I pour off and adding the same weight in water, in addition to the water I'll be adding to equal the weight of flour or do I not need to be as thorough as that?