happyThe social game companies are fashionable now that Electronic Arts bought Playfish for as much as $400 million. One of the newest challengers enjoying attention is Crowdstar International, which last week launched its second successful Facebook game, Happy Pets.

Burligame, Calif.-based Crowdstar already has 30 million month active users on Facebook, ranking it as the sixth largest developer on Facebook. That is thanks to the success of Happy Aquarium, which has 27 million users, according to AppData. The company expects Happy Pets, launched on Thursday, will pass a million daily active users soon.

The company was founded in 2008 by Suren Markosian, a web entrepreneur. Jeffrey Tseng also joined shortly after as a co-founder. Tseng is a familiar figure in video games. He was a co-founder of Secret Level, a San Francisco game developer which was bought for $15 million in 2006 by Sega. Secret Level went on to make console video games such as Golden Axe and Iron Man. The firm’s chairman is Peter Relan, who is also chairman of Aurora Feint.

The company has 20 employees, all of them focused on releasing a new Facebook game each month. The company has received less than $100,000 in seed funding from Relan.

In Happy Aquarium, users take care of fish. In Happy Pets, users adopt kittens and take care of them as they grow into cats. The company makes money via direct payments for virtual goods. It doesn’t use any offers, which have recently been tainted by a scandal over alleged scams.

The success didn’t happen overnight. Crowdstar also launched earlier games Know-It-All-Trivia, Save the Reef, and WWII. But Happy Aquarium is the first breakout hit. Relan says the company is now making profits of $1 million a month.