A couple of years ago I switched to Camco tsx, on our last trip the black tank valve was getting increasingly difficult top open. Maybe the make up of the Camco product being citrus based was the problem.
This summer I did the mineral oil soak and that freed it up some, subsequently I've gone back to the Aqua Magic crystals. The valve now operates smoothly like it was new, only thing that's changed is the treatment.
I use Piranha septic cleaner treatment. No issues ever
Piranha Holding Tank Cleaner | Super Seal Specialty Company (https://www.super-seal.com/piranha-holding-tank-cleaner)
I do the Geo Method
What is the Geo Method for RV Tanks? - TheRVgeeks.com (https://www.thervgeeks.com/geo-method-for-rv-tanks/)
English, when I search for Aqua Magic I get a toilet. Can you provide a link to your crystals, please?
15 coaches-never any chemicals used
My $.02...Happy Campers. Been using it religiously for 4 years full timing and zero vent odor even in summer heat with monthly dumps, and the grey water not so swampy smelling. Not a harsh chemical like most others I've tried...literally all of 'em. Economical. A scoop each dissolved in a glass of warm tap water in the loo and in sink after dump and then again at 1/2 tank level. A $55 tub lasts me a year or so. Woody.