This soil is used for aquarium plants too.
It's not really secret, but it took much time and experimentation to come up with a mixture that I am happy with. 1 part Playball, 2 parts Soilmaster Red (not the "Pro"), and 2 parts Turface Red, is a good recipe for me right now. I feel confident enough to answer questions and offer advice to other people that might be interested in trying this alternative method.
I like the organic fertilizer pellets I got from a bonsai guy on ebay, because I feel they may stay in the soil longer than chemicals.
I am weaning myself away from the softer potting soils for many reasons. No bugs, less compaction, and superior air permeability, are a few things keeping my plants happier. Also, the soil stays put when I water from above instead of floating away like perlite and lighter components do.
The 3 main ingredients I mix together have different characteristics that create a balance when combined. I tried using each substrate by itself, but obtained unsatisfactory results.
I encourage other people to post photos of their 7-pod/pot seedlings in this thread too. Try to keep the file size down to under 200k so this thread doesn't take forever to load. I plan to add several more pictures at regular intervals.