What is it okay to put in the gray tank?

Photomom said:

Stuff growing in there - salmonella, E. Coli, molds, etc. 

Would it be advisable to put some bleach in there?

@Ratkity?

I put a cap full of the same thing I use to treat the black water tank. I'm not sure but I think it is a Camco product.

I just put one of the same bio packets I use in the black tank. But ya, where's our microbiologist when we need one.

LOL @ScottG. The gray water only flows one direction - outward towards the drain valve. You can wash all sorts of things down the sink (food and hand washing stuff). The soap you use usually kills most microbes and if by chance you get an odor, you can run distilled vinegar down the drain and rinse it or use an RV gray tank deodorizer to get rid of the smell. 

Someone who full-times it uses the gray tank to its fullest, and those deodorizing packets are a good idea.