Dowflake for calcium??

[gregzz4]

The brown residue is apparently clay and is used to stabilize the salt so it doesn't clump
I used to get a lot of it when I was mixing my salt in warm water, but it's stopped since I started mixing my salt into cool water before turning on the heater
I used to use a brine shrimp net in my NSW before adding it to the DT 'cause it was that bad

I've seen no evidence of the clay in my DT system and get very little residue in my NSW tank now so I guess it just went into oblivion ....