Eating Pond Scum?!

So I just got a call from my roommate saying my dog got into this abandoned “water garden†in the backyard. She isn't too sure how long he was in it. It’s full of scum and really old stagnant water.
Is there anything I can do to hopefully minimize any sickness…I’m brining him to a friends cottage this weekend so the runs would not be good!! (not to mention I don't want him feeling sick!)
Thank you!

You might give your vet a call, to see what he suggests.

Feeding canned pumpkin should help firm up any runs that might ensue. I would check with your vet though. You'll want to read this: Blue Green Algae Toxicity in Dogs - LoveToKnow Dogs