if you can but you dont have to, if you have the access hole in the floor you can do it well enough with the tank in place. its just harder to acheive the drain and dry
no, you're wrong, While FSII has that effect thats not its primary purpose its also not disposed of in the hundereds of liters.. your out by at least an order of magnitude. Its now got eyes on it because of some naughty people who got caught out doing things they shouldt be doing for personal gain.
There are lots of things that will prevent snot but once youve got it its a pain to shift.
ITs got a few names I call it snot, or diesel clad. (mostly becasue Im crap at names, cant remember it and while I recognise it when I see it I cant pronounce it)

