Question on Mixed Saltwater.
 

Hope this is in the right topic. First a little background info. I have a small pico tank and replace about 80-90% of my water every two(2) days, plus a 20 gallon running for the fun of it. . I mix a five(5) gallon pail right after I do the water change. The salt mix I have been using since the start of this tank is Reef Crystals by Instant Ocean. I have a small power head keeping the water in a constant motion as well as a heater keeping the temp. around 77-79 F. Covered. I use only RO-DI water which comes from a 35 gallon container. Which also is heated and has an air stone in for motion and to keep it aerated. My question is, Is it "NORMAL" for the new mixed water to have a almost beige sandy type grit that eventually encrusts the pail that I have to take a scraper to get it off? I started noticing this after a few weeks of using the same pail. This is the first time I've used Ro-Di and also made up water in a holding container. I've wanted to ask this question for about two(2) years since I first noticed the gritty type film.

Thank you for your input.
Len

its normal, its calcium

Calcium??

Yup