I never have at least in the first week. I never even turn the lights on unless I'm checking on something or doing some aqua scaping. My reasoning for no skimming was to allow the numbers to run coarse without a interuption my a skimmer or other products (media). I like my numbers to sky rocket and that tells me that the steps are in place. I simply do water changes as need to bring the numbers back in check. Once my numbers are steady, I kick on the skimmer and lights on. After that, my hardiest fish go in. FYI, the stability by seachem has allowed me to cycle a tank in a week with no extreme numbers. I still use stability for an additive in my current DT.