Black Tank Chemicals for High Temperatures

When we are traveling, I empty the tank weekly. Since the sensors don't work, weekly seems to be fine for the 2 of us. All I can tell you is that when I tried to use just 2 ozs for a week, an odor would develop. With 4 ozs the week was fine. When traveling, I flush the tank regularly letting the flush go until the water is almost clear.

I plan to buy something and would really appreciate product recommendations. If you are happy with just using water. I'm not comfortable with that. We have been doing this since 2001 and have always used some sort of chemical.