Jean & Richard,
I buy at Walmart the blue Thetford liquid Campa Chem Natural formaldehyde free holding tank deodorant. It comes in 6 bottles per box. Also, I purchased from Camping World Potty Toddy Tabs. I add 1 bottle of the blue liquid to the charge, and 1 or 2 of the tablets. I don't have any problems with smells when I use these 2 products. Even in very hot weather, the smell is eliminated.
Give it a try. The 2 products are not very expensive so you are not out too much if you don't like them. :
???
Bob Strong