How long can I keep this gravel?

[Keedee]

So I got a bunch of free gravel from a friend of mine who was changing their aquariums around. I got enough for a 40 gallon tank but I only have a 20 gallon. I'm using this as material to help kick-start my cycling process with good bacteria - can I keep the excess gravel? For how long before the good bacteria wont be there any more/will die off. Right now it's all in buckets of water.

 

[Coyne]

As long as the water is oxygenated and you're adding an ammonia source, then it should stay alive for quite a while. So, hook up an air pump and hose and add some fish food (or pure ammonia, if you have some).

 

[Keedee]

I added ammonia and I was lucky to have a spare air pump/hose around. Thank you!