Seedling Watering - When to turn on bigger lights?

Got some seedlings going

about 8 days old

under florescents (long grow lights from wall mart on a shop light)

soil 1/3 vermiculite
1/3 pearlite
1/3 peat moss

they are about 3 inches tall

using fox farm grow big and big bloom

i have a 150 watt hps light and a 400 watt hps light

1. ive been watering every 2 days.. the soil is still a lil moist after 2 days.

Should i wait longer inbetween waterings?

2. When should i switch to my 150w hps and then when should i go to my 400 watt hps?

kiss-ass

lwt the soil dry out before watreing,and give them two weeks gefore the big lights.