Converting a tank and build thread?

[fl3xlinton]

Hey all I was wondering how difficult it would be to convert an old cichlids tank into a saltwater tank? And I also want to start a build thread I have no idea how to do that. I would appreciate all advice you can give.

 

[fl3xlinton]

The first picture is my already saltwater 40 gal aio and the second picture is my 65 y’all with cichlids in. My lfs will take them and sell them and give me in store credit for them.