We usually see this occur in pools equipped with salt systems. Most of the time the very fine flakes are minerals that have formed and attached themselves to the plates in the salt cell. The cell has a reversing mode to expel this calcium build up from the plates and keep the cell clean and in good working order. As this occurs the flakes peel off the plates and enter the return lines. When they reach the pool, they are blown onto the floor as you see in this picture. They need vacuumed, and in and of themselves, are harmless.
The fact that they are present is the concern. When the flakes form to the extent that you can see and vacuum them, it is an indication of high total dissolved solids (TDS) and is usually coupled with a high pH environment. Being on a well will increase the likeliness of this happening as top up water is constantly adding additional minerals and metals to the pool water. The antidote is to keep the pH in range (manually and / or with automation), continue and increase scale free dosages, and clean your filter more regularly. If the flakes do not stop in a couple weeks, a sequestering agent and treatment should be started.
Taking corrective action right away is important. If the scale continues to form it MAY instead form on the pool structure and fittings. This can cause discoloration to the pool and equipment. Consider these flakes a canary in the mine.
