Reef Chemistry Question of the Day #281: Alkalinity You May Not See

[Randy Holmes-Farley]

Reef Chemistry Question of the Day 281

All of the following are incorporated into commercial supplements. Which of the following will not boost alkalinity in a normal reef tank with regular dosing?

1. Calcium acetate
2. Calcium formate
3. Calcium polygluconate
4. Calcium carbonate
5. Calcium oxide
6. Calcium hydroxide

Good luck and Happy Reefing!

Previous reef chemistry question of the day:

Reef Chemistry Question of the Day #280: Which is the best analogy of ion spacing in seawater?

Reef Chemistry Question of the Day #280: Which of the following is the best analogy of ion spacing in seawater? A. The ions in seawater are spaced like a 20 ducks on a 1 acre pond B. The ions in seawater are spaced like 4 people on a 747 jet C. The ions in seawater are spaced like 2 ice...

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[jbrady429]

I'm going with calcium polygluconate. That would raise calcium levels but not alkalinity, I believe.

 

[Miami Reef]

Calcium carbonate. It is insoluble that won’t dissolve unless the pH gets very low (to the point where coral skeletons will slowly dissolve).

It would work in a calcium reactor, but just dosing it is like dosing the KorrallenZucht Coral Snow water clarifier.

 

[hunterallen40]

Calcium acetate -- isn't that what brightwell's reef code A contains? I'll guess that one then

Edit: nope. +1 for calcium carbonate

 

[Randy Holmes-Farley]

Anyone else before I give the answer?

 

[Miami Reef]

in a normal reef tank

Why do you keep saying “normal“ reef tank? What’s an abnormal reef tank?

I’m asking in a curious way. I noticed you say normal reef tank a lot in different scenarios.

 

[Randy Holmes-Farley]

Why do you keep saying “normal“ reef tank? What’s an abnormal reef tank?

I’m asking in a curious way. I noticed you say normal reef tank a lot in different scenarios.

That's a good question.

It's just my catch-all phrase to eliminate from consideration situations that may exist in other sorts of aquariums (freshwater, etc.) or natural waters (including weird ones like hydrothermal vents, etc.) or wastewater or whatever else someone might think of or google that may have a different answer than the conditions in a reef aquarium.

FWIW, one of the answers in this question changes if the answer is applied to a reef aquarium at pH 7.4 and an alk of 7 dKH. That would be an abnormal reef tank, IMO, so that would not be a correct answer.

 

[jbrady429]

I'm going with calcium polygluconate. That would raise calcium levels but not alkalinity, I believe.

I’m wrong about this. Randy pointed out in a previous post that the biological processes that cause corals to take up calcium from the polygluconate also produce alkalinity. There’s an important point to understand here, in that biological processes can add alkalinity to the tank in addition to what we’re intentionally dosing.

I’m going with calcium carbonate as well, as that precipitates out into a solid under “normal” aquarium conditions.

 

[Randy Holmes-Farley]

And the answer is:

All of the following are incorporated into commercial supplements. Which of the following will not boost alkalinity in a normal reef tank with regular dosing?

1. Calcium acetate
2. Calcium formate
3. Calcium polygluconate
4. Calcium carbonate
5. Calcium oxide
6. Calcium hydroxide

Calcium carbonate is supersaturated in normal seawater at any pH above about 7.7. Thus, if you add some, it will not dissolve.

All of the others add alkalinity. Some of them (formate, acetate, polygluconate) require metabolism by organisms to detect most or all of it.

Calcium oxide and calcium hydroxide (the hydrated form of calcium oxide0 are suitable for making limewater (kalkwasser).

 

[Troylee]

And the answer is:

All of the following are incorporated into commercial supplements. Which of the following will not boost alkalinity in a normal reef tank with regular dosing?

1. Calcium acetate
2. Calcium formate
3. Calcium polygluconate
4. Calcium carbonate
5. Calcium oxide
6. Calcium hydroxide

Calcium carbonate is supersaturated in normal seawater at any pH above about 7.7. Thus, if you add some, it will not dissolve.

All of the others add alkalinity. Some of them (formate, acetate, polygluconate) require metabolism by organisms to detect most or all of it.

Calcium oxide and calcium hydroxide (the hydrated form of calcium oxide0 are suitable for making limewater (kalkwasser).

Scared me for a minute! I read that wrong haha! I was like I use that every other day to clean my tank and I haven’t had any issues! I thought I was just lucky for a second.. I use that and mb7 to clean my water and rocks.. Sunny’s diy coral snow..