Need help mixing powder solution

[Randy Holmes-Farley]

I’m trying to raise it, not maintain. The AFR I’m dosing seems to keep up with consumption already, but I feel 1250 is a little low and I’d ideally would like to be at 1350. So I’m just trying to bring my baseline up 100ppm by adding the 235grams of powder I calculated.

How are you measuring that 1250 ppm and what is the salinity?

I know that is what you are trying to do, and it's fine to do it as long as magnesium is not a lot higher than you think.

I'm simply expressing the opinion that the 1250 ppm value noted may be subject to massive potential error, and 1250 ppm is not a big issue anyway. Much of the ocean where corals grow is near 1250 ppm magnesium.

At 24 mL per day of AFR added to 150 gallons, you are adding:

1.8 ppm calcium
0.04 dKH of alk
0.01 ppm of magnesium

The actual ongoing depletion of magnesium will be no higher than 0.2 ppm per day. Likely less. So to drop from 1300 ppm to 1250 ppm would take 250 days, assuming no water changes that would also add magnesium if the salt mix is at least 1300 ppm.


So if you have been doing this dosing for 250 day without water changes, the 1250 ppm is quite plausible and adding some is fine.

If you have not been doing it that long or have been doing water changes, then I expect the low value is either test error or low salinity.

The latter can be fixed by raising salinity or doing the addition you mention, but the former is the concern. What if magnesium is really already 1400 ppm and this value of 1250 ppm is test error?

 

[Jaybeastin]

I’m trying to raise it, not maintain. The AFR I’m dosing seems to keep up with consumption already, but I feel 1250 is a little low and I’d ideally would like to be at 1350. So I’m just trying to bring my baseline up 100ppm by adding the 235grams of powder I calculated.

Magnesium was right around mine. My LPS did not look happy . After slowly increasing my magnesium to 1300 and more later my LPS have looked more opened and happy already. I'm going to shoot around 1350-1400

 

[buruskeee]

How are you measuring that 1250 ppm and what is the salinity?

I know that is what you are trying to do, and it's fine to do it as long as magnesium is not a lot higher than you think.

I'm simply expressing the opinion that the 1250 ppm value noted may be subject to massive potential error, and 1250 ppm is not a big issue anyway. Much of the ocean where corals grow is near 1250 ppm magnesium.

At 24 mL per day of AFR added to 150 gallons, you are adding:

1.8 ppm calcium
0.04 dKH of alk
0.01 ppm of magnesium

The actual ongoing depletion of magnesium will be no higher than 0.2 ppm per day. Likely less. So to drop from 1300 ppm to 1250 ppm would take 250 days, assuming no water changes that would also add magnesium if the salt mix is at least 1300 ppm.


So if you have been doing this dosing for 250 day without water changes, the 1250 ppm is quite plausible and adding some is fine.

If you have not been doing it that long or have been doing water changes, then I expect the low value is either test error or low salinity.

The latter can be fixed by raising salinity or doing the addition you mention, but the former is the concern. What if magnesium is really already 1400 ppm and this value of 1250 ppm is test error?

Thank you for the break down, I’ve been trying to find the amounts of major elements AFR actually adds - do you have the minor and trace breakdown too?

I have a Trident as well as a recent ICP to confirm my Trident’s data. I also have a Salifert test for mag (Hanna for Alk) that I’ll check against periodically, although it’s very hard to figure out if my endpoint is correct and there’s always random amounts of air in the syringe for the final reagent. When I test with Salifert, I see about 1350 (as long as that’s my worst case, I’m fine with a high if 1450).

I thought I was at 1350 for the last couple months, but calibrated my Trident after I got my ICP back, and after calibration it dropped 100ppm about dead on to what the ICP resulted (Nov 3rd test results). I figured now is the best time to raise and “chase” mag before the tank gets more established. Goal is to not let numbers (or chase numbers) change much to keep it constant and let corals adapt to my parameters so if any problems occur later, I can rule swings out.

 

[buruskeee]

what is the salinity

Sorry forgot to answer this in my reply. I keep my tank at 34.5ppt at 77.5°


Found the batch ICP test for my salt. So yeah I guess my Trident and ATI ICP test should be pretty accurate since I’m using 97% of the salt mix in relation to the test. Once I get mag to about 1350, my AFR dosing should keep it there and I shouldn’t have to worry about mag again after that. I just want to make sure my corrective dose will be safe to do. I’ve only done 100grams in a 1L volume that I added yesterday. I’m waiting for my Trident to test a few times before adding the next amount.

Name of product tested: Red Sea Salt Batch number: 1903230112

Tested element Units Acceptable Range Batch Analysis pH 8.2-8.5 8.20 Total Alkalinity meq/l 2.7 - 3 2.89 Calcium | Ca mg/l 415-445 436 Magnesium | Mg mg/l 1240-1320 1310 Sulfur | S mg/l 870-930 902 Potassium | K mg/l 375-405 405 Bromine | Br mg/l 60-70 64.09 Strontium | Sr mg/l 8-9 8.35 Boron | B mg/l 4-4.4 4.11 Total ammonium | NH4/NH3 mg/l ≤0.1 ≤0.1 Nitrate | NO3 mg/l ≤0.3 ≤0.3 Phosphate| PO4 mg/l ≤0.03 ≤0.03

All values relates to minimum sample size (as per mixing instructions) of salt mixed in R.O. water to salinity of 35.5 ppt.