>>928762The spirulina is salty, but I'd say it's less salty than a potato chip. There isn't much taste otherwise. I don't find a need to desalinate it further.
Uh, oh, math. It's very quick to multiply. I'll be up front with you and say I'm not sure about the answer. It's really easy to culture, so you could probably get a test batch going strong for under $50 US and answer some of your own questions. Worst case is you have algae culture experience under your belt.