Starting phyto
 

Can a culture be started from commercial, refrigerated "live" phyto? or is it better to start with single species cultures?

It's probably easier to start with a culture disc but even if you start with a blended product you will probably find that one strain out competes the others. Usually nanochlopsis.

Yes you can start a culture with the refigerated stuff. It's a good way to get your feet wet. Like midgetwaiter says, eventually one strain will outcompete the others.