Raising seedlings and rooting new clones is one of the few times when compact fluorescent lights (CFLs) can be more advantageous than a HID lighting set up. This is particularly true in the case of clones because you want them to be focusing on the development of new roots versus photosynthesis and the creation of new leaves. With that said, if you are using a strictly HID setup then metal halide (MH) bulbs are better for this stage than high-pressure sodium (HPS).
The lighting cycle for seedlings can be either 18/6, representing 18 hours of daylight and six hours of darkness, or it can be 16/8, but a full 24/0 lighting schedule is generally a bit overkill for seedlings. By comparison, new cuttings and young clones with underdeveloped roots should be on a 12/12 lighting cycle or 16/8 lighting cycle at most.
The reason clones don’t need nearly as much light as seedlings is because clones are supposed to be focused on developing new roots which happens below the soil, whereas exposure to light encourages them to focus their energies on photosynthesis and the creation and maintenance of new foliage. To further encourage new clones to create new roots it’s recommended to remove any large fan leaves or to trim them down substantially.
Seedlings and newly rooted clones alike can be kept under CFLs for several weeks if you aren’t ready to transplant them into full veg. Depending on the strength of your CFL set up, your plants will continue to grow and develop a larger root ball until you transplant them. Using CFLs also allows you to keep your light closer to your plants since the bulbs are much cooler.
Another option for lighting seedlings and clones is to use LEDs, although LED setups generally cost more. T5 lighting is another affordable method of lighting your seedlings are new clones; T5 lights are class of CFLs that come as long tube lights and are often sold as part of predesigned lighting kits. Some of the most reputable manufacturers of lighting and growing equipment include Sunmaster, High Tech Garden Supply (HTG Supply), Hortilux, and Lumatek.