In silent prayers, behind imam, do you recite a surah after fatiha?
It is mandatory for the followers praying behind an Imam to recite the fateha in the silent rakahs and silent prayers, without which your prayer is invalid.
It is not mandatory to recite another surah after fateha but you would lose the reward if you didn’t recite it. What is mandatory is to recite the fateha. Besides, what will you be doing standing there and not reciting anything?