DrewE wrote:
You don't actually have to use any chemicals in an RV tank, though they can be mighty helpful on cutting down on odors under some circumstances.
I wouldn't worry too much about upsetting the balance in a septic tank from RV holding tank treatment chemicals used in proper moderation. Septic systems see all sorts of household chemicals all the time, due to cleaning bathrooms, washing dishes, and other household tasks, and generally that causes no problems for them if they're properly designed and working correctly. Since not a few dump stations feed into (large) septic systems at RV parks, any tank treatment will be at least reasonably safe for them.
RV Holding tank chemicals are NOT for making it smell better. They are used the BREAK DOWN the solids. Doug