I've always used a latex black paint for my freshwater set-ups..Never painted the back of my salty's though.. I like the latex ..You can scrape it off the glass with minimal effort..
It doesnt matter what kind you roll or spray. Because it is on the backside of glass and you will be looking at it through more glass and water even flat paint will appear glossy and they all stick near the same as none are actually made for glass
I've used Rustoleum black glossy, oil-based, for the back glass, and Krylon flat black pray paint for the internal PVC. I did not scuff up (buff) the PVC first and over time the Krylon did begin to chip away, revealing the bright white underneath. No harm came to my inhabitants from the paint chipping though.