  Simulating dwarf galaxy halos in a reionizing Universe puts severe
constraints on the sub-grid model employed in the simulations. Using the same
sub-grid model that works for simulations without a UV-background (UVB) results
in gas poor galaxies that stop forming stars very early on, except for halos
with high masses. This is in strong disagreement with observed galaxies, which
are gas rich and star forming down to a much lower mass range. To resolve this
discrepancy, we ran a large suite of isolated dwarf galaxy simulations to
explore a wide variety of sub-grid models and parameters, including timing and
strength of the UVB, strength of the stellar feedback, and metallicity
dependent Pop III feedback. We compared these simulations to observed dwarf
galaxies by means of the baryonic Tully-Fisher relation (BTFR), which links the
baryonic content of a galaxy to the observationally determined strength of its
gravitational potential. We found that the results are robust to changes in the
UVB. The strength of the stellar feedback shifts the results on the BTFR, but
does not help to form gas rich galaxies at late redshifts. Only by including
Pop III feedback are we able to produce galaxies that lie on the observational
BTFR and that have neutral gas and ongoing star formation at redshift zero.
