Well I started them at 300 and they were baby baby seedlings....did great...went up to 400 after a week and they started looking sort of dark green. This was my very first hydro grow so I thought that was a pretty cool color (they WERE quite pretty bluish green) so I upped it to 500 the third week before I finally got a clue. I think I ended up keeping them at about 400 until they were about 5 weeks old. In blooming they were nute monsters!!