how big of a tank needed

[yanke]

hi
how big of a tank would I need for 5 discus that are about 12-17 cm big
I have a 3x18x20 and a 4x18x20
thanks yanke

[jimstreet]

I have 4 x 10-11cm in a 4x18x20 and plan to add another 2-4. My reading suggests 50L/adult fish.