I don't recommend cloning until the plant's at least a month (if ur gonna top or clone for sex). I normally wait til the moms are 2 months b4 taking cuts. As long as u have a bare minimum or 2 sets of leaves it should work. I tried toping a plant too young once. I cloned the top and it stuck but the "mom" was forever stunted. I was in soil and I realize hydro grows faster. If u have no experience cloning, I'd wait a bit honestly. The process is very simple but u don't want to mess up ur existing plant. Just as sure as I post this, some1 will com and tell u go for it and may even try to coach u thru it. Ultimately the decision is urs. U may wanna read this > When should I take clones from my plants? and peruse the threads a little more, That's my 2 cents. Good luck with ur grow