For a research project, I am trying to get either simulants, or real water parasites that have been inactivated (in particular Cryptosporidium and Giardia). I've found some options for actual crypto, like the Sterling parasitology lab at the University of Arizona. But they want 200 bucks per ml of the concentration of parasites that I would be working with...which could potentially work for certain parts of my research that only require small amounts (like the optical tweezing I mentioned in another thread), but for "bulk micro-separation" (another parallel project) I would need a more affordable substitute. And I still haven't found a source for Giardia. One thing that comes to mind as a possible simulant is yeast....It is a fungi, but doesn't it also form spores which are similar in size to crypto?