The best solution I found was through RVUgrades.com!
You can Purchase a Chemical called "Blue Streak" which comes with a small holding tank that attaches to the wall next to Toilet. It comes with hoses and fittings to cut and splice into your toilet hose direct so that every time you flush you automatically add this chemical in your black tank! This hookup comes with 3 bottles of chemical and tank for about $40.00. Very easy to install and will definitely reduce your chemical usages considerably. 3 bottles of chemical will last approximately 4-6 months! Smells like Baby Powder, water in Toilet stats pretty & Blue! I did not regret this purchase not too mention resolved the SMELLY PROBLEM ! ?? LSU