Auto-optimisation of model parameters to fit all continuum and line observations of ET Cha. The first row shows the evolution of some model parameters as function of generation (total gas mass M_gas  [M_⊙] , total dust mass M_dust  [M_⊙] , outer disk radius R_out [AU]). The two l.h.s. plots in the second row show the resulting χ for photometry and Spitzer spectrum. The other four plots shows the resulting line fluxes as labelled, where the orange bars indicate the observed line flux ranges with 1σ errors. At generation 94, the evolutionary strategy got stuck in an unsatisfactory solution (local minimum) with well-fitting SED, but very bad line fits χ_Line ≈ 5, i.e. a mean deviation between model and observed line fluxes of (e⁵ ≈ 150)σ. We have manually changed parameters at generation 95, increasing the disk mass by a factor 10. The evolutionary strategy then found a well-fitting model which can reproduce all available line and continuum observations within about 1σ on average.