Ask 'Dr. Spa' Q & A Message Board

Hello all,
I am new to this forum, and wanted to say thanks in advance to any and all answers! I have owned a Cal Spa tub for about a year now. I believe it is 500 gallons or so. I thought I had become pretty good at water maintenance over the past year. Last week I drained and filled my tub as I usually do, no soft water, rinsed and cleaned the tub, installed a brand new filter and filled the tub. After filling the tub, the balance looked pretty good, but PH was high, and this is always the case with my water here in TX. I added some PH down, installed a Nature2 mineral sanitizer. I followed the directions to add dichlor to activate. The water looked beautiful.. I did not use the tub for about three days while I was away.

When we entered the tub for the first time, all the inside surfaces of the hot tub felt like fine sandpaper. We wiped down the whole inside of the tub, and now the next day, it does not seem to be sticking on the walls like it did originally, but all the seats and the bottom of the tub has fine granulated particles, as if you dumped little piles of fine sand every where.

I am not sure if this makes much sense, but I have drained and filled the hot tub many times and not encountered this problem. I normally use Leisure Time liquid Bromine chemicals (Reserve and Renew system), and this is my first try with the Nature2 cleaner.
Two things I can think of....I forgot to add a metal defender, or whatever it is called when you refill to protect the pipes, and I did not think to rinse the new filter out before installing it.

Thank you for any inputs.

Tom