"SpongeBob SquarePants" is saturating the airwaves in Germany -- but not just because the yellow sea sponge and his sidekicks have captured the hearts of German children.

"SpongeBob Schwammkopf," ("SpongeBob Spongehead") as the cartoon is called in German, is the main weapon in a pitched battle between Viacom Inc., which is trying to establish its Nickelodeon channel in Germany, and a tough local competitor, Super RTL. Nickelodeon is running 18 hours of "SpongeBob" a week. Super RTL is showing about 10 hours.

Viacom has no one but itself to blame for the competition. After pulling the plug on a previous attempt to launch Nickelodeon in Germany in 1998, it sought to squeeze some revenue out of Europe's largest TV-viewer market by selling Super RTL the rights to some top Nickelodeon shows. Today, that decision appears short-sighted as Nick -- the most successful kids channel in the U.S. -- and its German rival fight anthropomorphic sea sponge with anthropomorphic sea sponge.

When Viacom returned to Germany, it offered to buy back the rights to "SpongeBob," but RTL, which is co-owned by Walt Disney Co. and RTL Group, part of Germany's Bertelsmann AG, wouldn't sell. "As far as parents are concerned, we believe Nickelodeon is an unknown brand," says Claude Schmit, managing director of Super RTL. "Children are used to watching SpongeBob on Super RTL."

Marcus Andorfer, general manager of Nickelodeon Germany, counters that Super RTL's strategy shows that "they are frightened" and that independent surveys show German children like the Nick brand more than Super RTL. But without exclusive use of its own shows, it won't be easy for Nickelodeon to overcome Super RTL's lead soon. About five times as many people, including 370,000 children, watch "SpongeBob" on Super RTL as watch it on Nickelodeon, according to Viacom figures.

In the year since its launch in September 2005, Nick Germany has attracted about 7.5% of three- to 13-year-old viewers during the day. Super RTL's ratings have slipped to about a 27% share of that audience from about 30% to 32% before Nickelodeon arrived, according to figures from both channels. The other children's channel, Kinderkanal, a joint venture of two public broadcasters, has been relatively stable at about 15%.

Germany is a notoriously tough market for children's television because many parents believe TV should promote learning instead of entertainment, people in the industry say. A survey of German parents by Disney found just 5% said they would let their children watch TV just for fun, a Disney spokeswoman says.

Viacom is trying different tactics this time to make Nickelodeon a success. It has several new shows that aren't available on Super RTL. Unusual for Germany, Nickelodeon is also showing TV programs with actors, not just cartoons, including one starring the niece of actress Julia Roberts, Emma Roberts. About 10% of its schedule is local German programs. The deal with RTL expires in 2011 so if German children haven't tired of SpongeBob by then, Nickelodeon will be able to show it exclusively.

The German launch is part of a Viacom strategy to get more growth from its international cable networks. As one of the world's largest television markets, with a taste for Nickelodeon shows, Germany was a clear choice for expansion, company executives say.

To re-enter Germany, Viacom bought a small Cologne-based television network in 2004 for $379.5 million, put German voices and titles on many of its U.S. shows, including "The Angry Beavers" ("Die Biber Br¨¹der"), and began broadcasting in September 2005. It plans to add a comedy channel next year.

But Nickelodeon's launch provoked Super RTL, which had been largely unchallenged in Germany's kids TV. In the months ahead of Nickelodeon's launch, Super RTL started showing two additional "SpongeBob" episodes in the morning. Super RTL still shows three episodes a day during its 14 hours of daily broadcasting. Nick, which broadcasts 24 hours a day, shows eight episodes most days.

Super RTL also spent $2.5 million on what its managing director, Mr. Schmit, calls an "anti-Nick" advertising campaign. To play off the elections for a new German chancellor, Super RTL asked children to vote for their own children's chancellor from a list of Super RTL characters, including SpongeBob. It plugged the vote in newspaper, television and billboard ads, as well as on the Internet. Andy Larkin of the Canadian cartoon "What's With Andy?" won.

Viacom countered with its own marketing campaign, which it says cost several million euros. Over the summer, Nickelodeon hired a barge on the Rhine with actors dressed as Nickelodeon characters, including one in a SpongeBob suit. It visited eight cities, and about 18,000 children went on board.

So far, media buyers say, Nickelodeon has a long way to go to achieve its goal of unseating Super RTL as the top children's channel. "But we have seen a movement to the better in recent months," says Andreas Schmitt, a board director at WPP Group PLC's MindShare agency. Mr. Schmitt has booked advertising time on Nickelodeon for toy-maker Mattel Inc.