Is it safe too............?

#1
I have a friend thats giving me a plain 20gallon thats in good shape, been in a closet for so many years.It has nothing tho
and I know a place where i can possibly buy a elicpse 2 hood system for it for 20$ but it's used and it was used for saltwater? could i still  use it for clear water ?
or woudl u recommend keeping it as saltwater?
I'm a rookie as it is not sure if i'm even close to being ready for saltwater !!

Rd