Well I'll tell you about my "session"

I had no lotion or anything on my feet.

water was fresh tap water {city}
machines were new - not much rust yet I'd guess

put feet in water - machine turned on - 10 min slight yellowing in water
they added some salt at times - brings up the conductivity - 2.0 is the optimum number for that.

I watched and nothing odd appeared in the water at those times when the salt was added.
20 mins more of an orangeish tint

after the 40 mins- "results"
medium orange water with some floating particles.
some possible mucus - I do have a slight allergy/sinus stuffiness
3 tiny dark linear particles - the list says possibly metal
one clearish linear thing - list says possible parasite - I know yuck- but the lady said she had long thready things when she did hers -eeewww!

they do use a disposable liner just so you know that part.

anyway it was interesting to give it a try and I am glad it didn't turn totally yucky black