Randy - Question on your Magnesium DIY

[02tts]

Hi Randy, first off my hat goes off to you. I have read many of your articles (who's chemistry references are way, way past my basic level of understanding but they have been a monumental asset in providing essential guidance in setting up my tanks throughout my many years in the hobby, and for that I truly thank you.

I had a question about your DIY magnesium recipe. I cannot for the life of me find Dead Sea Works MAG Flakes anywhere. I live in Florida which makes it even harder as you can imagine as we do not normally have icing or snow issues down here. Anyway, is there another product that you would recommend as a suitable substitute for MAG Flakes? I know BRS sells it but it's rather pricey given what I have seen MAG Flakes 50# lbs being sold for, which is around $50-$60 which includes ground shipping, the issue is I can't find anyone that has it, the only place I found only sells it by a pallet, which if I actually has the room to keep all those bags I'd buy it and just hang on to it.

I greatly appreciate your help and I thank in advance.

 

[Dr. Reef Verified Sponsor]

i have been using Safe Step mag chloride 8300 mixed with Epsom salt with no issues. (over 1 yrs now). 7 1/4 cups of ice melt and 2/3 cup of Epsom salt mixed in 1 gal of rodi water.

 

[chipmunkofdoom2]

Ice melter is cheaper, but you really should consider how much you'll be dosing when you're making this purchasing decision. An average reef tank uses such little magnesium that I don't think it's worth going through the trouble to source driveway ice melter over BRS chemicals.

Per Randy's article on Mg, let's say your tank has relatively high consumption of calcium and carbonate: it uses 16 ppm Ca and over 2 dKh of carbonate alkalinity per day. In one entire year, your magnesium will only drop by 149 ppm assuming those rates of calcium and alkalinity consumption. In the same time, you will have dosed 5,840 ppm of calcium and 817 dKh of carbonate alkalinity. So the amount of magnesium used by a reef tank is relatively small in most cases to begin with.

To raise your magnesium by 149 ppm, you only need 473 g of dry magnesium chloride, which is just over one pound. Dowflake is about a dollar per pound, while the BRS supplements are about $3.30 per pound for the 7 pound bags. If you need a pound of it per year, the Dowflake is cheaper at just over a dollar for magnesium for the year. But, if all you need is a pound, the BRS stuff is only about $3.30 per year. The savings of buying 50lbs of ice melter over BRS's supplements is just barely over two dollars a year in this scenario. Even if you assume that my math is off by 100%, the much more expensive BRS magnesium still only costs you $4 extra a year. Plus, that assumes you have high magnesium consumption in a large tank (100 gallons). Most reefers will actually use much less than this.

I personally don't think buying a 50# bag of MAGFlake is worth the trouble. Even at higher consumption rates, the BRS stuff is just not that expensive because of how little magnesium is used.

It's also worth noting that the manufacturer of MAG Flake explicitly recommends against putting MAG Flake in reef tanks. They do not claim or guarantee that this product will be safe in any way for reef aquaria.

 

[02tts]

Ice melter is cheaper, but you really should consider how much you'll be dosing when you're making this purchasing decision. An average reef tank uses such little magnesium that I don't think it's worth going through the trouble to source driveway ice melter over BRS chemicals.

Per Randy's article on Mg, let's say your tank has relatively high consumption of calcium and carbonate: it uses 16 ppm Ca and over 2 dKh of carbonate alkalinity per day. In one entire year, your magnesium will only drop by 149 ppm assuming those rates of calcium and alkalinity consumption. In the same time, you will have dosed 5,840 ppm of calcium and 817 dKh of carbonate alkalinity. So the amount of magnesium used by a reef tank is relatively small in most cases to begin with.

To raise your magnesium by 149 ppm, you only need 473 g of dry magnesium chloride, which is just over one pound. Dowflake is about a dollar per pound, while the BRS supplements are about $3.30 per pound for the 7 pound bags. If you need a pound of it per year, the Dowflake is cheaper at just over a dollar for magnesium for the year. But, if all you need is a pound, the BRS stuff is only about $3.30 per year. The savings of buying 50lbs of ice melter over BRS's supplements is just barely over two dollars a year in this scenario. Even if you assume that my math is off by 100%, the much more expensive BRS magnesium still only costs you $4 extra a year. Plus, that assumes you have high magnesium consumption in a large tank (100 gallons). Most reefers will actually use much less than this.

I personally don't think buying a 50# bag of MAGFlake is worth the trouble. Even at higher consumption rates, the BRS stuff is just not that expensive because of how little magnesium is used.

It's also worth noting that the manufacturer of MAG Flake explicitly recommends against putting MAG Flake in reef tanks. They do not claim or guarantee that this product will be safe in any way for reef aquaria.

Hmmm. I have a 500G of total water volume and I dose 170ml per day to keep it at 1350-1400. By that count, that's WAY more than 149 ppm in one year.

Obviously I must be doing something wrong then?

 

[chipmunkofdoom2]

Hmmm. I have a 500G of total water volume and I dose 170ml per day to keep it at 1350-1400. By that count, that's WAY more than 149 ppm in one year.

Obviously I must be doing something wrong then?

Your tank size is unusually large, so all the numbers are going to be necessarily bigger in your case. A 160 ml/day dose using a recipe like Randy's only contributes about 4 ppm of magnesium in a tank that size. That's higher than 149 ppm per year, but it might not be a problem.

How much calcium and alkalinity two part are you adding per day?

 

[02tts]

Your tank size is unusually large, so all the numbers are going to be necessarily bigger in your case. A 160 ml/day dose using a recipe like Randy's only contributes about 4 ppm of magnesium in a tank that size. That's higher than 149 ppm per year, but it might not be a problem.

How much calcium and alkalinity two part are you adding per day?

Dosing per day:

Calcium is dosed from 11pm-12am using a dosing pump.
Alkalinity is dosed from 1am to 10:30pm using a dosing pump.

Calcium: 270ml per day
Alkalinity: 700ml per day

The above maintains my tank values at 410-420 calcium and 8-8.2 alkalinity.
Calcium is measured using API test kit.
Magnesium is measured using Salifert test kit.
Alkalinity is measured using Hanna test kit.

I realize these are hobby kits, etc. but those are the values using the above kits.

This is a FOWLR system. There is probably 400-500lbs of pukani rock and is barely stocked at the moment. Not a new setup, it's been up and running for about 1.5 years now.

Not that it should matter for the Alk/Cal or Mag levels but I also dose vinegar, currently at 2ml per day during a 24-hour period.

 

[02tts]

i have been using Safe Step mag chloride 8300 mixed with Epsom salt with no issues. (over 1 yrs now). 7 1/4 cups of ice melt and 2/3 cup of Epsom salt mixed in 1 gal of rodi water.

Thanks. Have you measured it for ammonia? Any trace amounts of it?

 

[chipmunkofdoom2]

Calcium: 270ml per day
Alkalinity: 700ml per day

What two-part system are you using? There are exceptions, but in general, you should be dosing the same amount of the calcium and alkalinity parts daily.

Your system appears to be using a lot of calcium and carbonate alkalinity, especially for a FOWLR. Do you have a lot of coralline algae growth? This could explain the increased consumption of alkalinity and magnesium only.

Another thing worth mentioning, your calcium and alkalinity are pretty close natural seawater levels. Considering this and that it's a FOWLR system and how large the tank is, I personally would not attempt to keep magnesium too much higher than natural levels (~1,280 ppm).

 

[02tts]

Pls see next reply. This was in error.

 

[02tts]

What two-part system are you using? There are exceptions, but in general, you should be dosing the same amount of the calcium and alkalinity parts daily.

Your system appears to be using a lot of calcium and carbonate alkalinity, especially for a FOWLR. Do you have a lot of coralline algae growth? This could explain the increased consumption of alkalinity and magnesium only.

Another thing worth mentioning, your calcium and alkalinity are pretty close natural seawater levels. Considering this and that it's a FOWLR system and how large the tank is, I personally would not attempt to keep magnesium too much higher than natural levels (~1,280 ppm).

I’m using Randy’s recipe #1 for both alk and calcium. Using Dow pellets, using baking soda and baking it as instructed.

Assuming at 1300mag levels coraline should still grow?

I realize it’s usually 1:1 but it’s not the case in my tank. I have verified as I’ve stopped dosing for a few days and tested daily which alk and calcium drop by the levels I’m dosing.

There is no precipitate that I can see going on.

Now, tank has been running for 1.5 years, however; empty (fishless) for 12 months due to a velvet outbreak. During that time I did monthly water changes of 20% but I did not keep up with any levels, was not dosing and lights were off. I suspect that the consumption is due to coraline growth which seems to be manifesting itself on the Rocks, it hasn’t exploded yet but it’s steadily growing. I have some diatom which is probably slowing it down. So I think the alk and calcium consumption may be due to coraline. Why it’s not a 1:1 ratio I can’t explain and the chemistry behind it is beyond my understanding

 

[02tts]

Sorry for the double post. I’m using my phone and having some issues

 

[02tts]

Here is a picture of the tank from a couple of weeks ago but it’s hard to see the coraline growth because of the lighting That’s rights after I cleaned it during a water change on 8.11 that’s why the bottom sand is pretty clear. Right now there is some brown on there which I can’t figire out what fueling it since I feed every other day and have .02 phosphates.

 

[02tts]

Disregard part about no precipitate. I’ve just noticed that some of my sand is very clumpy. Just spent the last hour trying to break it all up.

So does that mean that there is too much dosing going on? Even though test kits say I’m on par?

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, doctor Foster and Smith also sells magnesium chloride. Last I checked they did not list a purity, but you can decide if you trust them.

 

[02tts]

FWIW, doctor Foster and Smith also sells magnesium chloride. Last I checked they did not list a purity, but you can decide if you trust them.

Thanks again.

 

[02tts]

FWIW, doctor Foster and Smith also sells magnesium chloride. Last I checked they did not list a purity, but you can decide if you trust them.

Any thoughts on the alk and ca consumption I’m seeing? Seems that test kits report proper reading but I am seeing clumping of the sand?