What the heck is consuming my alkalinity?

[ReefDreamz]

No corals, no coralline algae. Fully cycled 1 month old 200 gallon tank. Alk is reducing by an average of 0.15 dkh per day despite already dosing 2.7 grams Brightwell Alkalin8.3p per day. What is consuming alk? I don't see any precipitation forming on my pumps.

 

[Reefer Matt Verified Media Partner]

What salt are you using?

 

[Nate Chalk]

Rock and sand absorbing?

 

[ReefDreamz]

What salt are you using?

Brightwell NeoMarine. Salinity is 34.6

 

[ReefDreamz]

What salt are you using?

Brightwell NeoMarine. Salinity is 34.6

Rock and sand absorbing?

Is this common?

 

[Randy Holmes-Farley Verified Community Expert]

Is nitrate rising? That depletes alk.

Not sure I understand the amount mentioned. Is the with or without accounting for the additive?

 

[GoVols]

No corals, no coralline algae. Fully cycled 1 month old 200 gallon tank. Alk is reducing by an average of 0.15 dkh per day despite already dosing 2.7 grams Brightwell Alkalin8.3p per day. What is consuming alk? I don't see any precipitation forming on my pumps.

As Randy asked, are your nitrates on the rise?

 

[ReefDreamz]

Is nitrate rising? That depletes alk.

Not sure I understand the amount mentioned. Is the with or without accounting for the additive?

The alk is reducing by 0.15 dkh per day while already dosing 2.7 grams alkalin8.3p per day. The chart shown is while already dosing 2.7 grams alkalin8.3p per day. Nitrate isn't changing much.

 

[Reefer Matt Verified Media Partner]

I looked up online that your salt mix mixes up at 7.5 dkh alkalinity. Have you done any water changes recently?

 

[ReefDreamz]

I looked up online that your salt mix mixes up at 7.5 dkh alkalinity. Have you done any water changes recently?

No. No water change was performed during this time period.

 

[Reefer Matt Verified Media Partner]

The buffer you are using mentions that once the ph gets to 8.3 ph, then alkalinity will go up? Perhaps you are not using enough of the buffer.

Brightwell Aquatics - Alkalin 8.3-P

 

[ReefDreamz]

The buffer you are using mentions that once the ph gets to 8.3 ph, then alkalinity will go up? Perhaps you are not using enough of the buffer.

Brightwell Aquatics - Alkalin 8.3-P

I think you are interpreting it incorrectly.

• Helps increase pH stability in an aquarium by raising the alkalinity; continued addition raises
  pH until 8.3 is reached, at which point the pH remains unchanged and the alkalinity
  alone increases.

 

[Reefer Matt Verified Media Partner]

Is this true? My pH has never been above 7.95. Usually fluctuates between 7.8 and 7.9.

Not sure, as I don't use the product, but it mentioned it on the website in that link I posted. I like to use a salt mix that mixes up to the parameters I like to keep my coral in, without using buffers, etc.

 

[Neuratox]

I noticed this same thing happening about a month or two after my tank cycled. This lasted a week for me based on my reef log. During that time my phosphate went from 0.01 to 0.06. In my experience when the alk consumption stopped it was abrupt so suddenly my daily dosing caused it to spike, so watch out for that. This was about the same time that I started to see the appearance and bloom of cyano. Don't know if the two are related, but figured it was worth noting. I wish you the best in figuring out what is causing the issue. I never did for certain.

 

[Randy Holmes-Farley Verified Community Expert]

The buffer you are using mentions that once the ph gets to 8.3 ph, then alkalinity will go up? Perhaps you are not using enough of the buffer.

Brightwell Aquatics - Alkalin 8.3-P

It’s a simple alk additive. Ignore the pH 8.3 stuff. It’s intended to impress without saying anything significant. It is mostly bicarbonate and a little carbonate.

 

[ReefDreamz]

I believe I have figured out the problem but not what is causing it. My alk is precipitating out as calcium carbonate. I didn't notice the precipitate before because I was looking for a white precipitate but I expect this tan/brownish precipitate (picture below) is the calcium carbonate.

However, after reading this article: http://reefkeeping.com/issues/2005-07/rhf/index.php nothing sticks out to me as the reason.

My magnesium level has been steady for weeks at ~1400 ppm
My temperature has been very stable at 78.4 to 77.2
My pH fluctuates between 7.84 and 7.93 depending on if the windows are open

None of these numbers would indicate why I'm getting calcium carbonate precipitation, correct?

I have noticed that my calcium level (which fluctuates between 430 and 390) has an inverse relationship with my alkalinity level, if I dose alkalin8.3 my calcium level drops, if I dose calcium my alk level drops.

Also strange is that my alkalinity level seems to drop at the same rate all day everyday no matter when or if I dose alkalinity as if it's being consumed, but again I have no corals, no coralline algae and my nitrates have remained steady at ~15 ppm.

 

[ReefDreamz]

I still don't understand what is causing my alkalinity to drop. Any thoughts would be appreciated.

As a reminder

I have zero corals or coralline algae
Nitrate has not risen over this period and has remained at ~15 ppm
Magnesium has remained stable over this period at 1400 ppm
Temperature is stable at 78.4 to 77.2
My salinity is 34.6 ppm
pH ranges from 8.01 to 7.96 (after adding a CO2 scrubber, it used to be 7.93-7.84 before the scrubber)
I'm using Brightwell Neomarine salt which mixes to a dkh of 7.5
I have not done any water changes during this period
I have not noticed any precipitation on heaters or pumps during this period. After cleaning off powerheads they have remained spotless during this period.

I stopped dosing any calcium or alkalinity during the period shown in the graphs. Where is my alk going?

 

[Randy Holmes-Farley Verified Community Expert]

I expect it is calcium carbonate precipitation, which is common and often unnoticed. It does not imply a problem.

 

[ReefDreamz]

I expect it is calcium carbonate precipitation, which is common and often unnoticed. It does not imply a problem.

Thank you Randy I appreciate the confirmation. A further question, if I am suffering from calcium carbonate precipitation but I want to stabilize alk and calcium levels is there anything I can do? I was going to try to slowly start dosing some limewater. Would this be a pointless endeavor? Should I just continue to let my alk drop and not try and intervene?

 

[Dan_P]

No corals, no coralline algae. Fully cycled 1 month old 200 gallon tank. Alk is reducing by an average of 0.15 dkh per day despite already dosing 2.7 grams Brightwell Alkalin8.3p per day. What is consuming alk? I don't see any precipitation forming on my pumps.

You might not notice precipitation if it was occurring in the sand bed. What is the magnesium level?