The Sarriflex were a race who once attacked Coral City.
The Sarriflex were a humanoid race who resembled upright pugs and were possibly related to them. They had limited intelligence, leaving out words from sentences when speaking. (PROSE: Grand Theft Planet!)
The Sarriflex were a warrior race who had warships. After no metal remained on their home planet, they tried to drain strontilite from Splendorosa for their ships and weapons, but their plan was thwarted. (PROSE: Grand Theft Planet!)
At some point in their history, the Sarriflex became involved in a war that lasted for hundreds of years. They drained their home planet of metal to build warships and weapons, but when their supplies failed, they travelled to Splendorosa, where a metal called strontilite could be mined. They accidentally caught Coral City in a magnetic pocket, and lifted it from the ground, arousing the suspicion of the Tenth Doctor and Donna when they arrived.
When the Doctor located Volsairius Trefgar, he questioned him about the nature of the city, but Trefgar kicked him out. After learning that GeoCorp, the company Trefgar represented, was founded ten years earlier, when the city first began to float, Donna and the Doctor were taken to the Sarriflex ship. They found out that the Sarriflex planned to steal the entire planet to use the strontilite inside it to build new ships and weapons that could be activated from far away, but the Doctor teleported back to Splendorosa and sent out an electromagnetic pulse to disable the Sarriflex ship, causing it to drift into the sun. (PROSE: Grand Theft Planet!)