Clones should be directly under soft fluorescent or ambient lighting right away for 24 hours a day. There is no dark period needed for clones at all.
My Suggestion is make your own aerocloner. Stinkbud outlines the steps on his post here:
https://www.rollitup.org/hydroponics-aeroponics/116859-harvest-pound-every-three-weeks.html
So spend the $50 to make yourself an aerocloner and there is zero science and maintenance to getting 100% success without having to mist once or use any type of humidity dome. No more pre-soaking pellets. No more moldy pellets. No guess work. Hell, you don't even need to use rooting solution if you don't want to. There are hundreds of people that use an aerocloner with just tap water and get 100% rooting success with no maintenance.
Using an Aerocloner
We take our cuts as we are cleaning up our plants & place the cuts into water until they are ready to be dipped into hormone and placed in the aerocloner.
Once they are ready, we recut the clone's tip, dip into rooting hormone and place into the aerocloner.
We leave the aerocloner off until we have it full of clones so the hormone has a chance to absorb into the clone's stem.
Once they are in the aerocloner, we set the cycle timer for 1 minute on, 5 minutes off and walk away.
1-2 weeks later we have 100% rooted clones with absolutely no misting, no watering, no maintenance, no worry.
These clones will last up to 2 months in the aerocloner with no further fertilizer. Definitely one of my favorite things about using an aerocloner..
Building an aerocloner will be the best $50 you ever spent and that's a promise. And of course, a million people will tell you they get 100% rooting success with a million different intracacies of methods and I'm sure they are all telling the truth. This just happens to be the easiest, cleanest, and most care-free method of cloning.