Different regimes in which thermohaline convection occurs (shaded regions) are compared against simulations presented in this work (black points) in terms of the diffusivity ratio τ (characterizing the thermal diffusivity) and the density ratio R₀ (characterizing the stratification). Filled contours show the estimated Reynolds number of the flows (detailed in the main text). Thermohaline convection in oceans typically occurs with τ ∼ 10⁻²; in stars, the possible values of τ vary dramatically but are generally much smaller. Previous 3D simulations have explored τ ≳ 10⁻² extensively, while the present work considers simulations with much smaller τ.