Oh, and I might add that there's another person's criticism of the iolite here, for your info:
http://www.thegrowreport.com/Forums/showthread.php?t=7627&highlight=iolite
and here:
http://www.thegrowreport.com/Forums/showthread.php?t=7313&highlight=iolite
I'd be very interested to hear if anyone...