To add chlorine for daily use (not the soaking part) I'm wondering if it is possible to add a peristaltic stenner pump somewhere so I'm able to go away for 14 days without having someone to take care of spa and stil have a fc >2
I think you would have difficulty getting a Stenner with a low enough volume for a 400 gal spa. Were I you I would stick with tabs in a floater. The water in the spa should be changed several,time a year anyway, so CYA rise should not be a problem.
Perhaps, but so far tab's only was not good enough to maintain proper fc level. Perhaps now it will. I've cleaned the spa with ahh-some a few times. Also not complete satisfied with aqua finesse. Beside no proper fc level i also had some scaling spot's. That's why i decided to take care of my own and just use stuff that's recognizably so i'm able to correct without guessing.