Reef Crystals testing low Alk and Mag

[Jon0807]

I'll admit that I've kinda been slacking in the testing department. My new setup has been running for about 7 weeks and have done a couple of water changes and 1 parameter test. I can't remember the exact numbers but I remember the dKh was at least 8. I just tested everything today and saw that my alk and mag was really low.

Here's the test results
Salinity 1.025
dKh 7.0
Cal 480
Mag 1200
NO3 50

I kinda panicked and dosed Magnesium before I remembered I was planning a water change tomorrow. I have about 20 gallons of Reef Crystals mixed but it's been heated and mixed for about 2 weeks. I've been using it to change the water of my QT tank with plans on mixing a fresh batch for my DT water change. But I didn't go through it fast enough. I heard that heated saltwater can precipitate calcium so I decided to test everything. Here are the results

Salinity 1.026
dKh 7.0
Cal 480
Mag 1200

Identical to my DT!! Is this what you would expect from water that's been mixed and heated for about 2 weeks? Is there something wrong with my dKh and mag test kits? (both are Salifert and not expired). Or do I have a bad batch of Reef Crystals? I know that RC is supposed to mix at much higher levels than this.

As far as corals go, I only have softies and LPS and I don't dose anything except for my moment of panic and dosed mag.

[Xxero]

I test every batch of new saltwater that I use for my water changes, and I also use Reef Crystals. The Magnesium and Calcium numbers that you quoted are the readings that I usually get, but Alk usually tests at around 11dkh in the new RC saltwater. I imagine that yours has somewhat dropped from the 2 weeks of sitting around.

Despite listed numbers on packaging, I have read that manufacturers tend to skimp on Magnesium because of its expense.

[Jon0807]

Originally Posted by Xxero

I test every batch of new saltwater that I use for my water changes, and I also use Reef Crystals. The Magnesium and Calcium numbers that you quoted are the readings that I usually get, but Alk usually tests at around 11dkh in the new RC saltwater. I imagine that yours has somewhat dropped from the 2 weeks of sitting around.

Despite listed numbers on packaging, I have read that manufacturers tend to skimp on Magnesium because of its expense.

I don't often test Mag cause when I was using IO, it consistently tested really high, I'm talking 1500+ So I assumed RC would test the same. This is the first time I tested the mag in RC. I'll have to mix up a new batch and see what it comes out as. But that's a huge discrepancy if it does really test that low compared to their claims.

[Xxero]

Yeah, it's weird. I have a Red Sea Magnesium kit and Salifert, and I get the same readings from both.

I have always used Reef Crystals, in hopes of the higher numbers, but they lack in the Magnesium department. Most other mixes that I have tried do as well. Calcium is usually right around 500 though, and Alkalinity around 11dkh, which I like. But if you keep your system's Magnesium somewhere between 1400-1500ppm like me, and then add a batch of 1200ppm salt mix into it, your Mag will drop down below 1300ppm.

I use BRS 2 part and simply add more Mag to the new saltwater. I'm curious what the regular Instant Ocean numbers are though. I have a new batch of RC mixing right now, so I'll test it later and post those numbers.

[Xxero]

I feel like I am always chirping about Magnesium on here, but to me, it seems like the most important of the three: Mag/Alk/Cal. Because if your Magnesium isn't kept stable, then the other two begin to fluctuate. Plus, I feel that maintaining higher levels of Magnesium keeps some of the nuisance algae at bay, but that might just be wishful thinking.

[Tcox]

In my limited experience, I've found reef crystals to be somewhat inconsistent with mag and alk. My last box of reef crystals gave me 12kh, 1600mg, and 510 cal! I ended up switching to fritz rpm and have pretty good numbers now.

[Jon0807]

So apparently I tested Alk wrong. I didn't wait till the solution turned pink so I was a few drops short. I tested a fresh batch of RC. Here are the results

Salinity 1.026
Alk 9.6 dKH
Mag 1200
Cal 440

I'll throw the calcium results into user error. But the mag is still low. I've have a new box that I haven't opened yet but I still have a few more cups of salt in the last bag of the last box. It'll have to see how that test. Will I have to dose mag from now on if I'm consistently getting low mag results if I decide to stick with RC? Everything seems to be doing fine. Especially my duncan which is sprouting like 6 new heads all at once.

[homer1475]

I switched to regular old IO an test every batch I make. After 5 200G boxes it pretty much mixes up to ALK - 9.9, Cal - 400, and mag 1250.

I dose mag up to 1350, cal up to 420, and ALK down to 8.5.

[Xxero]

I just tested a 15 gallon batch out of the last bag out of a 200gal box of Reef Crystals, and got the following results (I keep my specific gravity at 1.025, so you can round these numbers up a bit for 1.026):

SG = 1.025
Magnesium = 1020ppm (Red Sea & Salifert)
Alkalinity = 11.4dkh (Hanna Checker)
Calcium = 430ppm (Red Sea)

I might follow Homer and just dose up regular Instant Ocean from now on.