Good Day I recently did a filter medium change on my pool from glass to sand when i have to add Alkalinty up to my pool a few days later I have a white residue on the pool floor to which i have to vacuum up  going through a lot of water my Ta at this moment is 70 just below the minimum I know if i add alkalinity up i will experience the same issue I never had this issue using  glass as a filter medium  please can you point me in the right direction as i am at a loss do i replace my filter medium from sand to glass I await your response