+1
In fact, the water softening pillow may actually make things worse for the fish. It is not hardness (calcium and magnesium ion concentration) itself that "soft water" fish dislike but total dissolved solids (TDS- total ion concentration), of which hardness is a component. Water softening pillows lower hardness but actually raise TDS; they replace each calcium or magnesium ion with two sodium ions, so your water is gaining salinity faster than it's losing hardness.