That's the way it always happens... I just scraped the bottom of the bucket today.
I'm still mixing and matching salts, so I couldn't go crazy with a bunch of buckets, but managed to order 1 and a bucket of Coralife as well. I'm planning on purchasing a small bucket of the Red Sea salt mix in the near future and giving that a shot as well.
The nice thing is that you can cut IO with just about any other salt if you need to boost up the Alk a little bit.