source of high calcium

[loggix]

hi new to forum, just have quick question about really high calcium
my tank is cycled, its about 9 wks old now, tested my water its over 800
went down to lfs they tested it same reading, they told me to do water changes did that, still high tested my r/o water normal, my tap water normal, they said it wouldnt hurt anything but like most newbies i have to know why, i use kent salt i contacted them they said they have some trace elements butnot enough to do that my salinity is stable at 1.022
giong through a diatom bloom on my sand just curious i guess
heres a rundown of my specs
20 gallon high tank
30 lbs of oolitic sand
20to 22 lbs of cycled figi rock
150 visitherm heater
coralife 2x65 pc
aquaclear 150 w/ purigen and floss
fluval w/ black diamond carbon
full cleaning crew
couple of cardinals
couple of small pieces of rainbow rock in sand
3 softies
1 powerhead so far
any ideas ? thanks