To answer the OP, I used NOTHING in my tanks for 9 years in my last coach and never saw any problems. It is poop, after all, it's not supposed to be clean! No odors, either. I guess I had a good vent system. I did add rotating vanes to the top of my vents and I think that helped a lot to prevent odors.
If ever there is a spilled few drops, just flush with plenty of water. I also keep a spray bottle of 2/3 water 1/3 bleach to use on all my water connections, and I can spray with that to sterilize anything I want to make clean. And I always wear strong rubber, (not thin latex) gloves when handling sewer hoses, and I wash them with sopa and water after use. .
Marc and Jill, Wellington FL
2013 Entegra Anthem 44SL