I've had my discus tank set up for over two years now. 20 months ago I purchased 50 cardinals, I am now down to my last 2. 18 months ago I inherited about 45 rummynose tetras (no idea how old they were at the time but they were adult size, I still have 25 of these. At the same time I inherited about 30 neons, these died off within about 12 months.
My opinion is that the rummynose do best in the 30 degree temperatures. They also school nicely and look good and bright.