IF the cycle is done yes you need to do water changes. IF you have CC substrate you need to vacuum it when doing water change, if you have decorative amounts of sand then I would stir it around with your hand a little and vacuum the water (NOT THE SAND).
Monitor PH, ALK, CAL, phosphates, nitrite and trate, and ammonia levels.
Trates will lower themselves IF you have a DSB, because in the non oxygen area is where the trates get turned into nitrogen to complete the cycle. that is where the water changes come in. You should do atleast 20% water changes, or smaller ones more often. I do a 20ish% every 14 days.
Trates wont get down to 0 UNLESS you are not overfeeding and you are doing regular water changes.