Authors: Jada Walters (University of Arizona), Kris Klein (University of Arizona), Emily Lichko (University of Chicago), James Juno (Princeton Plasma Physics Laboratory), Jason TenBarge (Princeton University)

Pressure-anisotropy driven instabilities are ubiquitous in weakly collisional plasmas such as the solar wind. Simulating proton-electron plasma systems to study pressure-anisotropy driven instabilities is computationally expensive for fully kinetic models, and hybrid models typically simplify the electron species to an isothermal, massless neutralizing fluid. We present the results of simulations using the 10-moment, multi-fluid model contained in the plasma simulation framework Gkeyll. The higher order moments and closure used for this model allow pressure anisotropy to develop in all species. Allowing a finite anisotropy enables the electrons to play a significant role in the saturation of the parallel proton firehose instability. We also explore the interplay of oblique and parallel firehose instabilities in 2D simulations.