question about phytoplankton cultures

[saf]

I am in the process of growing my own phytoplankton. I purchased a bag of water and culture that is already larger than what I could use up quickly, before I begin to grow more. How do I maintain a population of phyto to feed my 38 gallon tank alive w/out making more than I could ever use?

thanks for any advice!

Scott

[SeanT]

Throw some away.
Use the little remaining to start the next batch.

[saf]

That was what I was thinking but didn't know if anyone had a better idea.

How long does the culture last after maturing?(how long can you feed it?)