Yeah, that's a silver kill coil. The pink stuff might be algae or bacteria. The kill coil only works if the water circulates. If you don't run a PC for a few weeks, it won't prevent growth. If I'm right, you'll need to flush the loop with a biocide to kill the stuff before returning it to service.
As for draining a loop, that often depends on the configuration, but as a general rule, you open a hole in the loop and follow Newton's laws (e.g. flip the case upside-down and all around). Be careful not to spill water everywhere.