resealing tank questions

[smokinreefer]

Hey everyone,

so i picked up a used 120 to do a downgrade from my 180 at my parents house.

the silicone on the bottom of the tank looks great!
but the silicone on the 4 corner joints look dried up and worn down.

do i need to scrape all the silicone off? including the bottom? or can i just do the sides?

and from what i've read, i'm thinking i need to use scs1200 silicone.
where are you all getting that locally from?

thanks!