Google Crawling Site To Death

In the last month or so, Google has decided to just crawl my store to death, over and over, all day every day. It seems to just want to try out every single combination of Bloomreach facet possible. 20+ facets? Sure! Mix and match!

Does anybody have a good strategy or suggestions for Google over-crawling our store content?

I guess adding a /robots.txt would be the way to go hereā€¦ see robots.txt - Wikipedia and more.

A plugin exists to manage it from CMS, see Robots.txt plugin