Social Gaming Network has acquired (fluff)Friends, a Facebook virtual pet game maker. Terms of the deal were not disclosed.

Palo Alto, Calif.,-based SGN is in a race with Zynga to dominate Facebook games and it has been on an acquisition spree, buying small game developers who can land their applications on the top of the Facebook charts.

The (fluff)Friends game lets users adopt virtual pets, interact with their friends’ pets and compete to earn virtual currency. Users can choose from dozens of pets. Owners can purchase items and give them away. They can also create customizable habitats with virtual gold. SGN claims that the user involvement for (fluff)Friends is high. Since January, the revenue per spender has increased 192 percent and spend per transaction is up 143 percent. Eric Eldon noted its growth in a story in July.

Facebook shows that the game has a million monthly active users since its launch in 2007. It was created by Mike Sego, an engineer at Google.In July, SGN secured an investment from Amazon founder Jeff Bezos’ Bezos Expeditions and in May raised $15 million from Greylock Partners and Founders Fund. SGN’s games have attracted over a billion page views, 54 million applications installs and nearly 1.1 million daily active users across Facebook, Bebo, hi5, and MySpace.