I live in Spain and have a pool 6 mtr. x 12 mtr. x 1,5 mtr. and fill it with the water from my well. On the walls and floor I have many sharp Crystals (see photo). No one can tell me here what these crystals are and with what (chemical) I can remove them and what I have to do to prevent it. I let analyse the water from my well at an official laboratory and put the results with this message.
I often check the pool water put clorinetablets in it for the right level and about 2 times a season I have to put some PH-minor in the pool.
On the picture you see the crystals on the tiles and joints. The tiles are glassmozaik 2 cm. x 2 cm.