Yea only problem having low mag is if you Alk and Calcium are also low it will be harder for them to raise, but if your alk and calcium are where you want them then not as big of deal

So today I tested a fresh batch of reef crystal salt, it's been mixing for 24hrs now.
Alk 7.82 Dkh (Hanna)
Calcium 415ppm (Hanna)
Mag 980

So I guess that's why I'm having a hard time getting my mag up to 1350

Woah. That's really, really low. Did you roll the bucket before you opened it? RC has lots of room to allow the salt to settle out, but it also has lots of room to roll it. If that isn't the problem, that's gotta be a bad batch/bucket, or a bunk test kit.

Really , roll the bucket before you open it ?

Urban legend :)

Magnesium issue
 

Interesting! I ran into something similar but in the opposite direction.....mag tested approx 2000.

Rolling the bucket didn't affect the readings for me.

Manufacturer did replace the bucket after I sent them a sample to test.

I'm in the why worry camp, although I don't have a lot of valuable sps either. I haven't been testing for anything for quite some time, something I did more regularly when I was new in the hobby & so was my tank. With the passing years, my best test is observing how the livestock & coral I have are doing on a daily basis. Haven't had a major crash, some critters including coral have died, but in my case, chasing numbers has never really solved anything in that regard. Every once in a while I will throw some baked baking soda, epsom salt or calcium into my top off container.

I understand testing for Potassium is the latest gig?

I don't test, but take potassium every day. And MG. And Zn. :)

I'm exactly same. I don't even have any test kits.

Rolling salt buckets has been talked/laughed about lots on here. Don't bother:lol:

Unless you're at the top of a very big hill :) Could be fun!