Micka qualified for the men's 1500 m freestyle, as Czech Republic's youngest swimmer (aged 17), at the 2012 Summer Olympics in London, by eclipsing a FINA B-standard entry time of 15:28.49 from the European Junior Championships in Antwerp, Belgium. He challenged six other swimmers on the first heat, including two-time Olympian Ediz Yıldırımer of Turkey. Micka edged out Iceland's Anton Sveinn McKee to take a second spot by six hundredths of a second (0.06) in 15:29.34. Micka failed to advance into the final, as he placed twenty-fourth overall in the preliminaries.