Yes, bioballs will also be a nitrate factory if used as a wet/dry. So will LR
rubble. The difference is that LR
rubble is porous and has deep areas that become anoxic and house the bacteria that turn nitrite into nitrate. Some of the newer materials (ceramic rings, etc) are also supposed to have the same type of structure. Plastic bioballs do not, though some folks don't seem to have a problem with them. PWC
's can make up for a lot.