Becoming a first-time kalk user. Help!

[CenlaReefer]

BRS has a bulk magnesium supplement (magnesium chloride and magnesium sulfate) that says the following: "For use with kalkwasser, calcium reactors and occasional adjustments." My brother and I have been adding small amounts of magnesium to our kalkwasser solution according to our needs to keep our levels up according to our test kits. It has worked very well. Think of it- one top-off solution to keep up alkalinity, calcium, pH, and magnesium. Of course that only works if you have a system that doesn't include a large number of SPS corals. I was told that at least one company is producing a kalkwasser powder with magnesium already premixed in. What do you all think?

 

[Randy Holmes-Farley Verified Community Expert]

It is a poor idea. Seriously.

You should not add magnesium to limewater. It will immediately precipitate as magnesium hydroxide, which is very insoluble in limewater, reducing the alkalinity as well as removing the magnesium. I show that here:

Aquarium Chemistry: Magnesium And Strontium In Limewater ? Advanced Aquarist | Aquarist Magazine and Blog


The company that claims it (Brightwell) has some issues. First, their product actually has no more magnesium than the "pure" material that I used for years. It is likely just an impurity that they try to claim as a benefit (which it is not). That amount is also way too low to offset the needs of an aquarium using that amount of limewater.

That all said, the product from BRS is a fine magnesium additive. In fact, it is my DIY magnesium system. Just disoslve it in fresh wtaer ad add when needed (which is likely not often). This has more:

Do-It-Yourself Magnesium Supplements for the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com

 

[CenlaReefer]

Randy, this is helpful information. That is tood bad. I hoped for a one top-off solution fix. I read some of your fine article on use of magnesium. I will study it some more. I was aware of your write-up on kalkwasser, yet not of this one. It is magnificent that R2R has a resident chemist on the forum! Thanks so much!

 

[Mattyice008]

About to do my first kalk dose. Doing 1/2 tsp per gallon, which will be 2.5tsp(5gal rodi in top off bucket) how long should I let it sit after I mix?
E/ using ME coral's kalkwasser

 

[Chaz D]

I usually top of my tank with a little ro/di water, then the ATO takes a few hours before it kicks in.

 

[GainesvilleReef]

About to do my first kalk dose. Doing 1/2 tsp per gallon, which will be 2.5tsp(5gal rodi in top off bucket) how long should I let it sit after I mix?
E/ using ME coral's kalkwasser

The precip usually settles out within 15-30 minutes. It's just fine aragonite/sand. It won't hurt your tank except maybe fouling some filters and pumps. Don't over stir. The more air/CO2 you mix in the less effective it will be.

 

[Randy Holmes-Farley Verified Community Expert]

Randy, this is helpful information. That is tood bad. I hoped for a one top-off solution fix. I read some of your fine article on use of magnesium. I will study it some more. I was aware of your write-up on kalkwasser, yet not of this one. It is magnificent that R2R has a resident chemist on the forum! Thanks so much!

You're welcome and thanks.

 

[Randy Holmes-Farley Verified Community Expert]

About to do my first kalk dose. Doing 1/2 tsp per gallon, which will be 2.5tsp(5gal rodi in top off bucket) how long should I let it sit after I mix?
E/ using ME coral's kalkwasser

I usually let it sit overnight, but how fast it settles depends on the article size of the calcium hydroxide used and whether you add an excess (I usually do).

 

[Mattyice008]

Hey Randy, I added it last night, topped off with regular rodi to raise the water level, and by the looks of it, the ATO will probably kick on in an hour or two with the kalk added from last night. I only ended up adding 2tsp to about 4.5 gal of rodi in my bucket. I'll test parameters throughout the week.

 

[Randy Holmes-Farley Verified Community Expert]

The precip usually settles out within 15-30 minutes. It's just fine aragonite/sand. It won't hurt your tank except maybe fouling some filters and pumps. e.

Unless there's undissolved calcium hydroxide present.

 

[Randy Holmes-Farley Verified Community Expert]

Hey Randy, I added it last night, topped off with regular rodi to raise the water level, and by the looks of it, the ATO will probably kick on in an hour or two with the kalk added from last night. I only ended up adding 2tsp to about 4.5 gal of rodi in my bucket. I'll test parameters throughout the week.

Sounds like a good start.

 

[Mattyice008]

Ok Randy, here's the results a week after the first kalk dose


7/27 - added 2tsp to 4.5gal rodi

7/28 - Alk 11.2, calc 475, mag 1600

7/29 - 3g WC, alk 9.8, calc 440, mag 1560, pH 8.1

7/30 - PH 8.0, alk 9.5-9.8, calc 440-445, mag 1560, na 5ppm

7/31 - out of town
8/1 - out of town
8/2 - out of town (tank withdrawals started to set in)

8/3 - Ph 8.0, alk 8.7-9.1, calc 425-430, mag 1560, na 0



Observations:

-also noticed that over the past few days, it looks like that white film on top of the RO disappeared, and there is a white film on the bottom of the bucket, and a very small pile of what looks like powder, less then a tsp amount, in the middle.

- definitely looks like the pH avg has gone up slightly, but I would like a little more, so possibly adding a little more kalk.

-a few acans in the tank that haven't grown new heads in 6-7 months, but grown in size, have started growing new heads since adding the kalk.

What do you think? Upping the dose to 3.5tsp:5gal rodi?

 

[Randy Holmes-Farley Verified Community Expert]

What target alkalinity do you want to maintain?
I usually recommend 7-11 dKH.

 

[Mattyice008]

Originally I was going for 10dKH, but after talking to many people I want to go for 8.5-9dKH I think. Tank is 80% acans, 15% chalices, 5% other random lps. No sps or softies except for a few small palys.

 

[luxauterna]

Is the fluctuation in alk over those few days a normal thing when dosing kalk through ATO? I am about to finally dive into using an ATO along with kalk as well. I just purchased a Tunze osmolator and some kalk.

 

[Mattyice008]

I did a very minimal dose, orob didn't effect my tank too much. I believe adding a little more in the next dose will help keep the alk stable . I use red sea test kits, so there's a tiny amount of haziness around the exact alk/calc/mag levels

 

[luxauterna]

Ah gotcha. Makes sense

 

[Randy Holmes-Farley Verified Community Expert]

Originally I was going for 10dKH, but after talking to many people I want to go for 8.5-9dKH I think. Tank is 80% acans, 15% chalices, 5% other random lps. No sps or softies except for a few small palys.

If that is the goal, I would up it a little perhaps, but not a lot, then let it run longer to see what happens.

 

[Mattyice008]

If that is the goal, I would up it a little perhaps, but not a lot, then let it run longer to see what happens.

Ok, and throw out the white stuff that's on the bottom?

 

[Randy Holmes-Farley Verified Community Expert]

I'd just ignore it. It is likely calcium carbonate and magnesium hydroxide. Neither is an issue for the tank.