Vinegar or Baking soda

We too like to put the RV to bed with spotless tanks. On our way home from our last outing, we drain all tanks, fill them with a little soap and drive to the last spot. The morning we leave for home, we drain and fill them twice and then fill them about a 1/3 of the way and put a little more soap in them. We stop at the last dump station before we get home and drain them. Once home, I take the want and completely clean out anything left in the black and then we store them open. We do put little screen caps on so nothing can crawl in. Probably way over the top for most, but that is the way we have been doing it for years.