Reef crystals magnesium low. Is it my salinity or no ?

SaltISlife · Feb 15, 2020

Reef cryatals for the last bucket and 4 bags have been low in magnesium for me. Instead of the 1350 or 1330 or what not it always is for me. Its been in the 1220-1250 range. I noticed this back in dec and everytime i get a nee bag or bucket its the same thing.

I called instant ocean about it and they are mailing me 3 bags and a bucket as replacement since i showed them proof of purchase. Which i wasnt expecting.

But im wondering is it reef crystals or is it my refractometers ? I have two of them, one is older so i got a new one and calibrated both using BRS calibration fluid. The old one seems fine. However my calibration fluid is about 7 months old. I always put the top on after i use it. Maybe 1 or 2 times i had rhe top off for less than a minute but ya.

I calibrated using distilled water and it seems in check. Decided to pull my hydrometer out and with distilled water its reading 1.000 on the mark. But then when i check my tank its reading 1.0245. So 2 points below 1.0264. Decided to rinse it in tank water to be sure left over distilled isnt lowering salinity and its reading the same.

According to instant ocean 1.023 is 1200 mag, and 1.026 is 1350. So doing the mathwith 3 points, that means 1 point is 50 mag.. So 1.0245 should be reading at 1250.

Which as you guessed it.. is what my water with reef crystals has been at for a couple months using these refractometers.

Maybe im wrong, but it almost seems like the hydrometer is right by going off what the mag should be and the two refractometers are wrong.

What do you guys think ?

SaltISlife · Feb 15, 2020

I just mixed a 5g batch fresh bag. Put it at 1.026 on my refractometer calibrated.. and it reads 1.024 on the hydrometer.

Tested the mag and it was 1250. I raised salinity in the bucket to 1.026 on the hydrometer. Or 1.028 on the refractometer and the mag was reading 1370.

So either reef cryatals is wrong.. or my refractometers are off by 1 or 2 points.. What do you guys think ?

PatW · Feb 15, 2020

You can buy a reference solution for calibrating refractometers. it comes at 35 ppt. I check my refractometer if I suspect it is off a bit. If it is, it is easy enough to adjust it. You can get the stuff from Bulk Reef Supply and probably from you LFS.

SaltISlife · Feb 15, 2020

I have the BRS refracto juice. But its half empty maybe 6 months old. So im not sure if its accurate anymore. Starting to wonder if it evaporates slightly overtime giving inaccurate results.

Because i dont see how im still getting 1250 mag after 5 bags and 2 buckets now. I understand bad batchs happens but this many ? Thats why im beggining to wonder if its because the salinity is lower then i think it actually is.

I know hydrometers have a repuation for being inaccurate.. but if mine is reading 0 with distilled or ro water thrn it should be calibrated properly.. and that would be my tank really is at 1.0245. But i dunno..

I guess ill go to the local store and buy some more refracto juice to see