Not sure about in the USA, but in the UK it is really easy to find a starter culture from bird baths etc, basically the "red dust" in any small volume of water that <"regularly dries out and re-fills">. As soon as it is wet (and re-growing) it goes green and looks just like Chlorella. I assume you could dry the cultures out on a regular basis to avoid too much contamination, because it is a poor competitor.If I could easily culture Haematococcus pluvialis
It has just got more and more expensive. I used to like the <"red Astax crumb from TA Aquaculture in the UK,"> but they can't get it any more, because of the demand from the food industry for astaxanthin.If it weren't so expensive I'd also try feeding shrimp the astaxanthin powder sold as a supplement.