Any updates on this? I believe PK do so well with Chara because of it's high calcium content. They need the calcium for their shells or exoskeleton if that's the right word.
That's what Bob Lusk said when I asked why PK did so much better with Chara than Nitella, even though they look almost identical. He also noted that that 50 percent increase in BG biomass with PK shrimp observed by Dr Swingle was in unfed pond. Artificial feeding would likely reduce PK positive effects somewhat, though they are still a plus.