won't ever really "expire". If it stays in a sealed container then there is no gas exchange, the NSW
will have a high CO2
concentration which will drive the pH down. Also, without any movement and with the lowered pH some components of the NSW
may fall out of solution or precipitate that would normally stay in solution. Even if this does happen, if you buy a bucket, take it home, drop in a powerhead and aerate it overnight, everything should balance back out. If that is the case, I would check the water for pH, calcium and alk
before using just to be on the safe side.