As far as I know, just about any tapwater contains hair algae spores, so if you EVER used tapwater....there you go......this is why if you fill a bucket with water and put it out in the sun....hair algae will grow......came from the tap. Snail shells, rocks, actually any crustacean shell....etc etc etc.....there is basically no way to not introduce atleast a few spores of hair algae...don't bother trying. Corals bought inflated will contain spores....actually even deflated probably they have many spores.....see what I mean? One spore, and there you go. Aiptasia is a different story....you can actually keep these out if you are lucky.....hair algae? forget it. I would feel fine betting money that just about 100% of tanks fresh or salt have some hair algae spores.