Hi Steve - it is a sterilising fluid commonly used for baby bottles etc and in hospitals over here.
Milton | Milton Sterilising Fluid
I like it because it seems less harsh then bleach and probably rinses off easier. Infact you don't really have to rinse it off to even make it safe for babies, but I always do cos it takes 5 seconds and makes me feel like it is purer!
Another side of my thinks - do we even need to be so sterile?! These plants live in the middle of forests amongst a myriad of decomposing matter, bark, moss, animal droppings, fungi galore and more so are we being too fussy?