[Gnome]

Hexagonal flatback tank? very nice
for 20gal, I recommend to get only 1 discus( general rule for discus is 1disc/10gal), cause 2 non pair discus will stress each other. Cardinal tetra is very nice for discus tank mates, but german blue rams is the best w/ discus water parameter ( they like warm, soft and slighty acid ph water)
but if you're lucky to get breeding pair, go with it, and if you do get pair and you want to breed them, I suggest you to use very fine gravel or sand substrate or potted plant (no substrate) even better for easy cleaning purposes also no other tank mates, that only if you want to breed them, remember to do WC at least every week, but if you want to breed them, then frequent WC is a must!