This is only a big problem when using Zeus with MultiSpecies, because then GammaField is a float[size]. Otherwise, it's just a float.
Update 1: fixing a few mismatched deletes picked up with valgrind and another memory leak. The change in Grid_constructor.C fixes a leak that only happens for temp grids, like those that get created in Grid_StarParticleHandler.C. This is because they never get FillFluxesFromStorage called, which would free that memory.
Also, I should point out that I have tested this with a small cosmology run and the output is the same.