Salarians are a race of amphibians with a hyperactive personality. They think, move and act faster then most species. However, their fast way of life is due to the fact that most Salarians are lucky to live to 40. They often criticize other species for their sluggish and dull-witted personality, especially the Elcor.
Due to their constant research and experiments, the Salarians are often referred to as the Scientists of the Galaxy. While their military abilities cannot compare to that of the Humans or Turians, they are very good at espionage. They have Special Tasks Groups that are often used by the council to infiltrate enemy forces to gather Intel or assassinate threats to Citadel Space.
 Discovering the Citadel
The Salarians were the second species to discover the Citadel just decades after the Asari. The two species worked together in an attempt to unite the Galaxy. The Citadel Council was created with a member of both the Asari and the Salarians taking a seat on the council. As a sign of trust, the Salarians publicly released classified records on one of their top intelligence services known as The League of One. This put the lives of the League members in danger and they reacted by assassinating the top members of the Salarian Government. The League of One members were eventually hunted down and kill. As part of a collecting assignment in Mass Effect, you can discover various ID's of the League members on different planets.
 The Rise and Fall of the Krogan
Over the past 1,400 years, the Salarians have have left a major impact on the Krogan species. They were the first Citadel race to discover the Krogan at a time when the Citadel races were caught in a major war with the Rachni. The Salarians helped the Krogans by giving them the technology to discover the Mass Relays. They also helped them move from the harsh conditions of their home planet and relocated them to safer locations. This was all part of a plan to manipulate the Krogan into helping the Citadel races in the war against the Rachni. Away from the harsh conditions of their home planet, the Krogan population grew bigger every year, some Krogan could give birth to around 100 offspring at a time. Their high numbers, plus their physical appearance made them perfect soldiers, and within the centuries that followed, the Krogan managed to drive the Rachni into extinction.
The Krogans were thanked by the Council with an embassy and a monument in the Citadel for their part in the Rachni Wars. They were also given new planets to colonize.
Without the harsh conditions of their home planet, the Krogan population began to get out of control. In the centuries following the Rachni Wars the Krogan planets became over-populated and they started taking other planets colonized by Citadel species by force. When they took over the Asari planet of Lusia, the Citadel Council demanded they leave. The Krogan ambassador was furious and dared the Citadel races to try and take their worlds back. This led to the Krogan Rebellion.
During the Rebellion, the Turians were a new species to the Galaxy with a formidable Military behind them. They took the front line in the war against the Krogans while the Salarians tried to find a scientific way to end the War. They created a biological weapon known as the Genophage which infected every Krogan and meant that nearly every Krogan offspring would die in stillbirth. The Salrians were hesitant to use it because they knew it would eventually lead to Krogan extinction. However, when the Turians got hold of it they didn't hesitate to use it. In the years that followed the Krogan continued to fight until they realized that they were just speeding up the extinction process. They eventually surrendered and the Turians became they third race to join the Counicl for their help in the Rebellions.