Stir it up occasionally and when there seems to be a lot of brownish stuff (this is a judgement thing) then do a vacuum. If you are using dead rock to start only vacuum half or so of your sand at a time.
You’ll get a 50/50 answer on this topic.
Just keep in mind that when you vacuum up detritus, you take beneficial micro fauna as well, the point being, if you vacuum, only do 1/3 each time