Changing it out, sure, but that would kinda defeat the purpose of having them in the the first place. They're biological filters and you do not require this type of biological filter. You need the kind that is porous and high surface area without ample aeration - eg live rock rubble or something like SeaChem's Matrix.
If it looks like branches of a tree, it may be a type of gorgonian (Google for images). The thing you should be looking, or rather listening for, is a sharp clicking sound
