What’s dropping my ALK?

[96hundred]

Hello all, this is my first post and I’m new to R2R so please forgive me if I posted at the wrong place. I have a 10 gallon nano, that's coming up on 1 month. Tank cycled at 2 weeks. I have Carib sea life rock and seeded tank with about 1lbs of friend's established rock and some established media. 1lbs Aqua biomics live gulf sand, Carib sea live sand. I have a pair of Banggai Cardinals, I added pods with dosing some Oceanmagik phyto. No corals. There is no coralline algae in my tank, just some algae.

I was curious and wanted to see what my ALK was at and it's currently at 6.1 I use Red Sea salt (blue bucket) and tested my fresh made salt water at 7.8 ALK. I recently did a water change yesterday about 2 gallons. When my cycle was finished at the 2 week mark I did a 5 gallon water change to reduce nitrates. What's going on with my ALK?

 

[therootcause]

In the thread below, @Randy Holmes-Farley mentions that rising nitrates will deplete Alkalinity. I believe it possible that the microcrustaceans in your sand bed and rock may be consuming calcium and alkalinity. Do you have a clean up crew such as snails or hermit crabs? I don't see any in the photos but figured I would ask.

Other reefer wondering the same thing

Additional post regarding this relationship

What is the salinity and pH of your system?

 

[Randy Holmes-Farley]

The purple on the rock is real corallne? If so, that can use a lot of alk.

Precipitation of calcium carbonate on sand and rock in a new tank can also consume alk.

 

[ReefDreamz]

It's normal. When my tank was brand new with only dry rock and sand and no corals or coralline it was consuming around 0.25 dkh per day of alkalinity with no visible precipitation. The only explanation I ever heard was that the alk is being absorbed by the sand bed.

 

[dadnjesse]

Double check the Salinity and the calibration of your device.

 

[96hundred]

In the thread below, @Randy Holmes-Farley mentions that rising nitrates will deplete Alkalinity. I believe it possible that the microcrustaceans in your sand bed and rock may be consuming calcium and alkalinity. Do you have a clean up crew such as snails or hermit crabs? I don't see any in the photos but figured I would ask.

Other reefer wondering the same thing

Additional post regarding this relationship

What is the salinity and pH of your system?

Thank you for the threads. I currently have 1 trochus snail, I see mini feather dusters. PH is at 8 and salinity is 35.3ppt. Yesterday I did a little under a gallon water change and my ALK stayed the same. Would it take much more to raise it by water change?

 

[96hundred]

The purple on the rock is real corallne? If so, that can use a lot of alk.

Precipitation of calcium carbonate on sand and rock in a new tank can also consume alk.

It is not real coralline. Do I just let my tank ride out and stabilize itself? Say if I want to add a soft coral sometime in the near future and my ALK is still at 6.

 

[96hundred]

It's normal. When my tank was brand new with only dry rock and sand and no corals or coralline it was consuming around 0.25 dkh per day of alkalinity with no visible precipitation. The only explanation I ever heard was that the alk is being absorbed by the sand bed.

I’m guessing the tank needs to mature in order for everything to stabilize? Or is that why people dose? I would like to just only keep it simple and do water changes. As I replied to another member. I did a 10% water change yesterday and alk stayed the same and didn’t rise. Would it have to take more to raise it? With water changes that is.

 

[96hundred]

Double check the Salinity and the calibration of your device.

I use a Hana salinity checker and I calibrated it at 35ppt. I’m at 35.3ppt right now.

 

[therootcause]

I think the long and short of it is most people are not checking Alkalinity at 1 month.

In re-reading your initial post, you're doing EVERYTHING right. Keep feeding the Banngai's and control nitrates with water changes. Let the tank continue to mature. I'm curious, is that a glass lily pipe on the left side down to a canister filter or some sort of sump and if so, what media and filtration is out of site?

Yes, you can add a soft coral at any point, but that means when dinos, diatoms, and algae begin to form as the tank continues to mature you will need to maintain lighting for the coral's sake adn wont be able to greatly reduce the light cycle. If I were you I would find a few more interesting inverts like a halloween hermit crab to add in the interim.

I think its a very clean design that you have created with the rimless/frameless tank and the open sand bed to the right and the front.

 

[blecki]

I saw this tank on reddit. Someone there pointed out that the process of producing nitrate consumes alk. It can be quite surprising just how much alk that process uses!

 

[therootcause]

I saw this tank on reddit. Someone there pointed out that the process of producing nitrate consumes alk. It can be quite surprising just how much alk that process uses!

I just checked Reddit to find the thread and it's funny that OP got the same answer on R2R and Reddit from two different people.

 

[blecki]

Well he would have gotten it from me but someone beat me to it. Alk won't stabilize until you have some organic process consuming nitrate at the same rate it is produced. If you're relying on water changes to remove nitrate then you also need to dose alk to replenish what's lost.

 

[Randy Holmes-Farley]

I just checked Reddit to find the thread and it's funny that OP got the same answer on R2R and Reddit from two different people.

I don’t know about Reddit, but I can assure you this is a simple fact with a simple answer and there’s no alternative facts about it.

Production of 50 ppm of nitrate from ammonia consumes exactly 2.3 dKH. I did not get that number from someone else. I calculated it based on the chemistry involved:

When Do Calcium and Alkalinity Demand Not Exactly Balance? by Randy Holmes-Farley - Reefkeeping.com


Alkalinity Decline in the Nitrogen Cycle

One of the best known chemical cycles in aquaria is the nitrogen cycle. In it, ammonia excreted by fish and other organisms is converted into nitrate. This conversion produces acid, H+ (or uses alkalinity depending on how one chooses to look at it), as shown in equation 1:


(1) NH3 + 2O2 —>NO3- + H+ + H2O

For each ammonia molecule converted into nitrate, one hydrogen ion (H+) is produced. If nitrate is allowed to accumulate to 50 ppm, the addition of this acid will deplete 0.8 meq/L (2.3 dKH) of alkalinity.

However, the news is not all bad. When this nitrate proceeds further along the nitrogen cycle, depleted alkalinity is returned in exactly the amount lost. For example, if the nitrate is allowed to be converted into N2 in a sand bed, one of the products is bicarbonate, as shown in equation 2 (below) for the breakdown of glucose and nitrate under typical anoxic conditions as might happen in a deep sand bed:

(2) 4NO3- + 5/6 C6H12O6 (glucose) + 4H2O —> 2 N2 + 7H2O + 4HCO3- + CO2
In equation 2 we see that exactly one bicarbonate ion is produced for each nitrate ion consumed. Consequently, the alkalinity gain is 0.8 meq/L (2.3 dKH) for every 50 ppm of nitrate consumed.

Likewise, equation 3 (below) shows the uptake of nitrate and CO2into macroalgae to form typical organic molecules:

(3) 122 CO2 + 122 H2O + 16 NO3- —> C106H260O106N16 + 138 O2 + 16 HCO3-
Again, one bicarbonate ion is produced for each nitrate ion consumed.

It turns out that as long as the nitrate concentration is stable, regardless of its actual value, there is no ongoing net depletion of alkalinity. Of course, alkalinity was depleted to reach that value, but once it stabilizes, there is no continuing alkalinity depletion because the export processes described above are exactly balancing the depletion from nitrification (the conversion of ammonia to nitrate).

There are, however, circumstances where the alkalinity is lost in the conversion of ammonia to nitrate, and is never returned. The most likely scenario to be important in reef aquaria is when nitrate is removed through water changes. In that case, each water change takes out some nitrate, and if the system produces nitrate to get back to some stable level, the alkalinity again becomes depleted.

 

[Randy Holmes-Farley]

It is not real coralline. Do I just let my tank ride out and stabilize itself? Say if I want to add a soft coral sometime in the near future and my ALK is still at 6.

I’d add baking soda to maintain 7 dKH.

 

[96hundred]

I think the long and short of it is most people are not checking Alkalinity at 1 month.

In re-reading your initial post, you're doing EVERYTHING right. Keep feeding the Banngai's and control nitrates with water changes. Let the tank continue to mature. I'm curious, is that a glass lily pipe on the left side down to a canister filter or some sort of sump and if so, what media and filtration is out of site?

Yes, you can add a soft coral at any point, but that means when dinos, diatoms, and algae begin to form as the tank continues to mature you will need to maintain lighting for the coral's sake adn wont be able to greatly reduce the light cycle. If I were you I would find a few more interesting inverts like a halloween hermit crab to add in the interim.

I think its a very clean design that you have created with the rimless/frameless tank and the open sand bed to the right and the front.

It is a glass lily pipe to an Oase thermo 100 canister filter. I'm using the stock sponges it came with but i'm think of switching over to filter floss. There seachem matrix with some established media from a friend's tank. I plan to get more CUC this payday as my tank has more algae growing on rocks and sand bed. Thank you for the compliment! I greatly appreciate it.

 

[96hundred]

Well he would have gotten it from me but someone beat me to it. Alk won't stabilize until you have some organic process consuming nitrate at the same rate it is produced. If you're relying on water changes to remove nitrate then you also need to dose alk to replenish what's lost.

Organic process consuming nitrate as in live stock? Water changes alone wouldn't replinish ALK alone until it stabilizes right?

 

[96hundred]

I’d add baking soda to maintain 7 dKH.

I've heard to do it slowly and not more than 1.4dkh a day correct?

 

[Randy Holmes-Farley]

I don't know about the 1.4 dKH number, but if the alk is about 6 dKH, I'd take a couple of days to raise it to 7 dKH using baking soda (not other products).

i would not try to raise it higher than 7 dKH for a while in cause precipitation is the issue.