Xeniid soft corals are sessile animals that rhythmically pulse their tentacles. The pulsing behavior is unusual in that it is not for locomotion, and there is evidence that these corals do minimal feeding. Experimental work has led to the current hypothesis that this pulsing behavior mixes the surrounding fluid to facilitate the photosynthesis of their symbiotic algae, their main energy source. This work aims to understand the purpose of this behavior by modeling the pulsing as an elastic-fluid interaction. I will present two-dimensional and three-dimensional simulations of these soft corals. The two-dimensional work uses the classical immersed boundary method, developed by Charles Peskin, which assumes the elastic structure is infinitely thin and massless with a prescribed motion. The two-dimensional simulations include an analysis of the fluid mixing and a photosynthesis model coupled to the fluid-structure interaction. The recent three-dimensional work will include using the immersed boundary finite element method developed by Boyce Griffith, which allows for a fully three-dimensional elastic structure in the fluid governed by fundamental solid mechanics. Here the motion is not prescribed, the pulsing motion is instead driven by muscle contraction modeled as active tension.