If you have an overflow box cleaning the sponge probably kills much more pods than water changes (unless you change at night and in the dark pods usually hide or at the very least are clinging to a surface). I save about 10 amphipods evertime I clean the sponge but some just seal there fate by going deeper into the sponge where I cant get em. They get a final shake over fuge and whatever's left has to suffer the torcher of sponge cleaning.