Depending on the final growing substrate you wish to use in our hydroponics system, you have a range of possible choices for the propagation medium. In hydro cannabis plantations rockwool is often used, due to its relative versatility, availability and price.
Another material suitable for cannabis seed germination and cuttings propagation is coco. Available in all sort of forms, it comes even in dedicated preformed rings, perfect for placing a seed inside. As in soil, the seed will sprout for itself and cutting will get adapted, but you can greatly increase the chances of that happening faster, at better rate of success and making young plants healthy, with well developed root system.
The key to successful propagation is using root enzymes - be it in powder, fluid or gel form - they allow the baby plant to produce strong roots without unnecessary effort, leaving more energy to grow healthy, which always leads to better and bigger yields of top quality marijuana.