Can it be converted?

as far as i know, no chain tensioner currently on the market can stand up to the backwards pressure of decelerating with the pedals, therefore if a frame has vertical dropouts and you want to run it fixed your options are limited to a white ENO hub, which i use and would happily recommend, or an excentriker bottom bracket (i think hubjub and charlie the bikemonger have them), which i think takes a 24mm hollowtech 2 type crankset. hope that helps.

Or magic ratio.