a summary rating;
Pure sphagnum moss +++ (unchopped grew better but chopped easier to tpl
Pure sphagnum moss over a layer of perlite (fine chopped) +++
Peat over perlite ---
Peat/sphag. over perlite +
Peat/sphag./sand over perlite ++
Pure perlite ++ (Survivors look good but 50% plants didn't make it.)