I have been growing cultures of H. pluvialis for several years and still haven’t figured out what exactly they like to grow optimally. I make have tried a media called “Optimized Haematococcus Medium” with mixed results. I also grow it at the temperature and light recommendations suggested for the best growth. However, this algae is still quite slow growing and never reaches high cell densities. This slow growth can lead to issues, namely contamination by other algae species. I recently had an issue of contamination which may have came in undetectable quantities in the original culture and only now reached noticeable density. This requires a re-isolation of the original H. pluvialis culture, a process that can take several months.
On the upside of my slow growing HP cultures, is high astaxanthin production. In my cultures I notice cells that are not quite in the full red/resting phase but still seem to be dividing and growing. The motile phase is barely present. Most other cultures of algae are much more straight forward to grow, but I feel it is worth my time to work on perfecting HP cultivation.