Water Storage and Element Precipate

Back Story:
I have a 55 gallon plastic drum that I have cleaned, cut a small hole in the top and I store salt water in my basement. I only use R/O water and just switched to IO Reef Crystals. I have a small garden pond pump inside that keeps everything nice and stirred up. However I have recently had some concern. I have had a FOWLR system up until I just added MH lighting and now I have some Zoa's... my water husbandry in the past was lacking, however for the last 2-3 months I have been doing weekly to twice weekly water changes and once a day feedings and began dosing 2 part. My water params have been the best I have ever had. SG-1.025 Nitrates - 0, PH 8.4, DKH- 9-10. However My calcium is stuck around 340-360 all the time, the highest it has ever gotten is 380. I believe my MG is low however I have to order a test kit as none of my LFS have them...

Real Question:
So my question is will the storage of the saltwater in my basement holding tank cause magnesium to precipate out? should long term storage be avoided to prevent element loss? any ideas or thoughts? Everywhere I have looked is about SG changes due to evaporation, that is easy to rectify, but what about the trace stuff?

 

Why not mix the salt 24 hours before doing a WC? You could have 2 drums and pump RO/DI into the second to mix your salt. That way it would stay fresh.

 

Thanks for the quick reply; I work a lot and am away from the house for most of the day and usually everyday. I like having it premixed so that my wc's take less time, I have a spigot on the bottom of the barrel and I just my 5 gallon buckets under and fill them up. It makes it really easy to do wc's and keeps me doing them because it easy. I think having to mix again would create double the workload. I am just curious if I am creating an element shortage. I am attempting to get everything dialed in before I upgrade to more difficult to keep species of coral.

 

I would test the SW in the 55 drum and see where the levels are at. What salinity is the drum water?

 

it is at 1.025 also...

 

Ok, as mentioned, test the calc, mag, and alk levels in the water change water. IIRC at 1.026 Reef Crystals should be at 455 calc, 1355 mag, and alk around 12 dkh. Your should test around 440, 1300, & 11.5 respectively at 1.025.