Can the old millstone be used to sit on the bottom of the lotus pond? Does it affect feng shui at home?

It is no problem to use a millstone as the base of the fish tank itself, but the position of the fish tank is strictly required. If you put it in the right position, you can avoid misfortune, but if you put it in the wrong position, it will be bad. Since you believe in Feng Shui, I suggest you find a master to help you go to the scene to see where it is suitable!