My options are:
Topsoil (it does dirty the water but the mudskipper isn't effected at all)
Pond mud (Indian mudskippers live near rivers as well, so that would probably work I think)
Mud from the river (if they let me take any, lol)
Clay soil from home depot
I think that the refugium mud is more like potting soil and won't work in the mudskipper tank, but I think that if I rinse the top soil out somehow it won't dirty up the tank. What does AC think?