I don't put anything in my tanks except liquid Calgon and laundry soap.
Then once a year treatment with RV-Digest-It before I put it way.
Three years old now and have dry and hookup camped 209 days to date.
No smell, ever.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW