As coral reefs continue to experience more frequent and intense stress, the processes of recovery will become increasingly important in determining average reef state. Recovery is contingent on density-dependent processes during early life-history stages which may severely limit population growth and survival. Synchronous mass spawning is a mechanism used by most corals to maximise fertilisation. The success of spawning depends on the density of fecund colonies in an area, the size-based quantities of gametes released, and cross-fertilisation between gametes. So-called Allee effects can occur if insufficient gametes are present in the water column and colonies become reproductively isolated, being unable to contribute to population dynamics. We explored the density-dependent processes driving coral reproduction and assessed how different sperm concentrations and contact times between sperm and eggs influenced fertilisation success for four phylogenetically and functionally diverse coral taxa on the Great Barrier Reef and Western Australia (Acropora spp. X 2, Merulinidae x 2). Early results indicate that fertilisation success is optimised at high sperm concentrations (>104 sperm/mL) and longer contact times (>30 seconds), but the extent of these relationships is species-specific. Results are fundamental to parameterising fertilization models that will inform the density and colony sizes necessary to keep coral populations reproductively viable and functional across different reef environments.