seedlings in rockwool and peat...when to take humidity dome off?

I have some seedlings in peat plugs and rockwool cubes. They have just sprouted and are reaching up for light. How long should I keep the humidity dome on them? they already have roots coming out the bottom of both substrates

any ideas?

Take the dome off now. Seedlings do not need high humidity, only cuttings need a prolonged period of high humidity. The best time to take the dome off would have been when the younglings broke the surface. What is important for seedlings is stable temprature, they love it nice and warm ,75f to 85f is a nice range to keep them in.

Yep, remove the dome when the seedlings first break the surface. Leaving the humidity too high after this point can actually cause your seedling to rot.