Alkalinity question

[Anirban]

I am observing a unique trend. My alkalinity gradually increases from 8.5 to 11-12 over a period of 5 days. I don't have any clue about this. But this is a steady trend happens every time without any failure. Anyone has any idea? My corals are growing including SPS every other parameter looks almost great,

pH-7.9
Temp-80
Cal-440
Mag-1340
PO4-0 (Hanna)
Nitrate-2-5ppm

 

[JimWelsh]

All by itself? No dosing, kalk in topoff, or calcium reactor?

 

[Anirban]

Actually without dosing....

I add biweekly Acropower, Pohl xtra special and KZ B balance(everyday)

 

[DannyB]

Have you tested the Kh of those 3 additives?

 

[deerhunter06]

alk just doesn't rise on its own, You have to be adding it some how.

 

[Anirban]

Not yet but the point is everyday 2ml of B balance increases the alkalinity from 8.5-12 in 6-7days is hard to believe. Actually this time I skipped it for 3 days in between thinking that but still it increases???

 

[Anirban]

alk just doesn't rise on its own, You have to be adding it some how.

Exactly and that what I wanted to know. How is dissolved CO2 level linked with alkalinity? I am thinking of doing some experiment lets see.

 

[deerhunter06]

Exactly and that what I wanted to know. How is dissolved CO2 level linked with alkalinity? I am thinking of doing some experiment lets see.

You aren't one of those people that does daily water changes are you?

 

[Anirban]

You aren't one of those people that does daily water changes are you?

Ha ha ...no once a week and 20% thats all. I use tropic marin Pro.

 

[deerhunter06]

I have no idea. Maybe you got a bad batch of salt with high Alk, you measure it before it goes in? How long has it been going on? Good question for randy. I'm stumped

 

[Anirban]

I have no idea. Maybe you got a bad batch of salt with high Alk, you measure it before it goes in? How long has it been going on? Good question for randy. I'm stumped

No salt is good as I measured after making it...reads-8.5 . Then added to the tank reads again and its 9.3 then after 6 days now its 12. As the tank alkalinity is already high so the water change was not being able to pull it down to 8.5 but 9 or 9.5.

 

[DannyB]

Maybe the lower pH is releasing carbonate from the sand and rock

 

[Anirban]

Maybe the lower pH is releasing carbonate from the sand and rock

So I started an experiment to understand the condition. I put two gallons of tank water and added in a glass bottle. Added acropower, B balance and Pohls xtra special and also a wooden aerator. I took the alkalinity reading and will check it after an hour, overnight and 24 hour. Lets see how this works?

 

[JimWelsh]

How are you measuring alkalinity?

 

[Anirban]

How are you measuring alkalinity?

Hanna

 

[Randy Holmes-Farley Verified Community Expert]

The most common ways that alkalinity rises in reef tanks that I have seen comes from either tap water to replace evaporation, or artificial live rock that is releasing hydroxide.

If nitrate is being reduced, that can also add to alkalinity, although it would have to be a big drop pretty fast to see what you see.

Any of these seem possible?

 

[Anirban]

The most common ways that alkalinity rises in reef tanks that I have seen comes from either tap water to replace evaporation, or artificial live rock that is releasing hydroxide.

If nitrate is being reduced, that can also add to alkalinity, although it would have to be a big drop pretty fast to see what you see.

Any of these seem possible?

Randy can you please explain the nitrate and alkalinity correlation?

 

[Randy Holmes-Farley Verified Community Expert]

Randy can you please explain the nitrate and alkalinity correlation?

Sure.

When organisms metabolize organics to ammonia and then to nitrate, alkalinity is consumed.

Then if it is taken up by algae or bacteria (or corals), htat same amount of alkalintiy is returned to the system.

So if you start with elevated nitrate and it is consumed, alk will tend to rise.

I show that chemically in the article below. Production of H+ depletes alkalinity

http://www.reefedition.com/nitrate-in-the-reef-aquarium/

from it:


Most of the nitrate present in the ocean results from the recycling of organic materials. The degradation of plankton, for example, provides nitrate. This can be shown in a simplified chemical equation describing what happens when organic “food” is digested with oxygen:

(CH2O)106(NH3)16(H3PO4) + 138 O2 → 106 CO2 + 122 H2O + 19 H+ + PO43- + 16 NO3–

which in words reads as:

plankton + oxygen → carbon dioxide + water + hydrogen ion + phosphate + nitrate

When nitrate is consumed, the exact reverse reaction takes place.

 

[Anirban]

Sure.

When organisms metabolize organics to ammonia and then to nitrate, alkalinity is consumed.

Then if it is taken up by algae or bacteria (or corals), htat same amount of alkalintiy is returned to the system.

So if you start with elevated nitrate and it is consumed, alk will tend to rise.

I show that chemically in the article below. Production of H+ depletes alkalinity

http://www.reefedition.com/nitrate-in-the-reef-aquarium/

from it:


Most of the nitrate present in the ocean results from the recycling of organic materials. The degradation of plankton, for example, provides nitrate. This can be shown in a simplified chemical equation describing what happens when organic “food” is digested with oxygen:

(CH2O)106(NH3)16(H3PO4) + 138 O2 → 106 CO2 + 122 H2O + 19 H+ + PO43- + 16 NO3–

which in words reads as:

plankton + oxygen → carbon dioxide + water + hydrogen ion + phosphate + nitrate

When nitrate is consumed, the exact reverse reaction takes place.

@Randy Holmes-Farley so I read all of the article. Now, I have few questions.

1. My system generally runs with a steady NO3 of 5-10 ppm. So to keep my alkalinity low or steady (like 8dkH) what should be my prime measurement? Looks like my denitrification process is more than efficient and now I need to slow it down a bit.Any good idea how to do that?

2. What is the best and efficient way to take out dissolve CO2 from the water?

 

[Salty1962]

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