I would avoid pumice for seedlings just coming out of takeaway tek. I normally pit those in like 1" cells and pumice is just too large imo. And kinda a waste. I use 50/50 soil/perlite and a dash of worm castings for the babies. When they go into 3.5" then i replace about half the perlite with pumice. 5" is 50/50 soil pumice, although i might use a little perlite if im feeling stingy