Before you buy a whole bag. Make sure your shrimps like it first, otherwise even a 1/2lb bag will be awhile to use up and will go bad by the time you reach 1/2 way. All my shrimps love it
I bought a few varieties of flakes from Angelsplus and in addition to the ziploc bags being much heavier and opaque, they included a silica gel packet.I suggest getting a silica gel packet (I save mine when I find them in things I buy) and use them when storing food long term.
I can't answer your question on the wafers, but it's not a question of "going bad", per se. It's more a question of "going stale" and end up feeding your fish essentially hollow food.I didnt realize these would go bad. Whats the life on dried spirulina wafers?