Soft corals live off of their zozanthellea algae that lives in side them through photosynthesis as do all corals. The zozanthellea however feeds of of micro plankton in your water. So depending on the mouth size of your coral depends on what you feed them. Take example of softies and zoas will more than likely eat phyto feast made by reef nutrition and sps
will eat oyster feast by the same company.
Silversides are small fish 4-6" fish that can be fed to carnivorous fish and nems as a food source instead of live foods