How many Tetras do you have? I would say you could keep about 5 discus in an empty tank (at least that's what i was thinking for my 46 bowfront) but you'd have to lower the number because of the other fish. Her is a link that i found useful.
I was thinking about 3 or 4 discus, but the more i look into it the more im against the idea. I want to keep something that ive not kept before, but i think discus will need too much time, which i may struggle with at times. any ideas at other fish i could keep? i dont want anything that gets too big, that another thing hat is putting me off too.