I really like this purigen.

  • We are currently upgrading MFK. thanks! -neo
Ive got a crap load sitting in a bucket for the past 6 or 7 months. Think its safe to use. Been submerged btw
As long as it can recharge it should work.
 
I love the stuff too.

Be careful when opening the container to put it in bags. Mine smelled like massive crotch rot and stunk up the room for a day. Not sure if that's normal, but at least the stuff works!
 
MonsterFishKeepers.com