One of my boys had green slime for several days, and I took him to a
vet(not his usual she was on vacation).  He started treating him for ECE.
After almost 2 weeks of treating him for ECE and giving him supportive care
he wasn't getting any better, so I took him to his regular vet.  It turned
out he had a single cell parasite called jardia(not sure of the spelling).
After 2 weeks of treatment he is perfectly healthy again.  The vet said
green slime isn't necessarily ECE, and ECE isn't quite as prevelent as it
once was, so you may want to take him to the vet to have them check for
other parasites in the stool so they're ruled out and you know it's ECE.
[Posted in FML issue 2938]