Red slime algae is a cyanobacteria that froms in tanks that have accessive nutrients. It is common to have small patches of red slime in your tank, but when it takes off their is a problem.
What are the measurements in your tank?
Size of the tank?
Last water change?
Number of fish?
Do you have any old carbon that might be leaching organic compounds back into the water?
Finally, you can buy antibiotic in order to kill the slime algae, but this treatment should only be done when the problem becomes very bad! You need to find the root of the problem.