I am a newbie myself but from what I have read here, you want to wait until your Ammonia and Nitrite have gone down to 0. At that point you will have high Nitrate. The only way to get the Nitrate down below 20 (which is recommended) is a PWC
(partial water change). At least that is the way I understand it. I am at the same stage on my tank. As of last night my Ammonia and Nitrite were nearing 0 and my Nitrate was 160. I am thinking I am just about ready for the PWC
. I hope someone corrects me if any of this is wrong.