  We present GalMC (Acquaviva et al 2011), our publicly available Markov Chain
Monte Carlo algorithm for SED fitting, show the results obtained for a stacked
sample of Lyman Alpha Emitting galaxies at z ~ 3, and discuss the dependence of
the inferred SED parameters on the assumptions made in modeling the stellar
populations. We also introduce SpeedyMC, a version of GalMC based on
interpolation of pre-computed template libraries. While the flexibility and
number of SED fitting parameters is reduced with respect to GalMC, the average
running time decreases by a factor of 20,000, enabling SED fitting of each
galaxy in about one second on a 2.2GHz MacBook Pro laptop, and making SpeedyMC
the ideal instrument to analyze data from large photometric galaxy surveys.
