  We study fluctuation conductivity in a single crystal of
BaFe$_{1.9}$Ni$_{0.1}$As$_2$ superconductor ($T_c$ = 20 K) as a function of
temperature and applied magnetic field. Magneto-conductivity curves, $\Delta
\sigma$ vs. $T$, were analyzed in terms of -1/(dln($\Delta \sigma$)/d$T$) vs.
$T$ plots, which allow to study different fluctuations regimes and to estimate
exponent values and temperature widths of each regime. The analysis of
magneto-conductivity curves evidence the existence of only two fluctuations
regimes, a possible critical one (of glass-like type) going from the
irreversible temperature to above $T_c(H)$ followed by Aslamazov-Larkin
fluctuations in the Gaussian regime.
