Why is my Alkalinity going down?

[Sinkers]

Hi guys,

I have noticed my alkalinity is going down by about 0.1 per day (0.6 over 1 week). What could be causing this, and what should I do about it?

Tank is a 25G waterbox, about 6 weeks old. I am currently experiencing my initial diatom bloom.

I have 3 small Zoa frags, a small Blasto frag, small Cyphastrea frag and a Duncan frag with about 10-11 heads.

Parameters;
Alkalinity = 6.8
Salinity = 1.025
Phosphates = 0.02
Nitrates = 11.1
Calcium = 405
Magnesium = 1305

 

[Randy Holmes-Farley Verified Community Expert]

That is a normal and very low depletion rate. It comes from nitrate increasing, nonbiological precipitation of calcium carbonate, and some consumption by organisms. Even snails consume alk to make their shells, though folks rarely discuss that.

 

[Sinkers]

That is a normal and very low depletion rate. It comes from nitrate increasing, nonbiological precipitation of calcium carbonate, and some consumption by organisms. Even snails consume alk to make their shells, though folks rarely discuss that.

Makes sense. Appreciate the information.

Will it just keep depleting indefinitely? What measures should I be taking to make sure it doesn't get too low?

I'm guessing 10% water changes won't increase it by much, will it? My new saltwater tests at 8.8 DkH

 

[Knucker]

Makes sense. Appreciate the information.

Is it necessary or advised to be dosing this early on? Or should I just replenish some of the alkalinity via water changes? Doing only 10% water changes I'm guessing wouldn't increase it by much, but my new saltwater tests at 8.8DKH.

You can use an Alk additive. Honestly baking soda works in a pinch.

 

[Sinkers]

You can use an Alk additive. Honestly baking soda works in a pinch.

I have seen baking soda mentioned. How do you dose it and how much do you use?

I was planning to dose all for reef in the future once I have enough corals using up more than I can replenish with water changes. I just didn't think I would need to dose anything so soon.

 

[Knucker]

I wouldn't use baking soda unless you are desperate. It works but it's hard to does accurately.

 

[Randy Holmes-Farley Verified Community Expert]

Makes sense. Appreciate the information.

Will it just keep depleting indefinitely? What measures should I be taking to make sure it doesn't get too low?

I'm guessing 10% water changes won't increase it by much, will it? My new saltwater tests at 8.8 DkH

If the tank is 7 dKH and the new salt mix is 8.8 dKH, a 10% change boosts alk by 0.18 dKH, so it helps but won’t offset 0.1 dKH decline.

 

[rishma]

I wouldn't use baking soda unless you are desperate. It works but it's hard to does accurately.

What makes you say that?

 

[Randy Holmes-Farley Verified Community Expert]

I agree that baking soda is a good choice. No hobby product is “better” in a scenario like this.

 

[Sinkers]

I agree that baking soda is a good choice. No hobby product is “better” in a scenario like this.

Is it better to raise it slowly initially, or can I just dose it back up to where it should be sitting? And then work out a small dose to maintain it going forward.

 

[Randy Holmes-Farley Verified Community Expert]

Is it better to raise it slowly initially, or can I just dose it back up to where it should be sitting? And then work out a small dose to maintain it going forward.

Depends on your target. To 7 dKH instantly, anything higher, bring it up slowly.

 

[Reef Puncher]

That is a normal and very low depletion rate. It comes from nitrate increasing, nonbiological precipitation of calcium carbonate, and some consumption by organisms. Even snails consume alk to make their shells, though folks rarely discuss that.

for 2 weeks my alk was stable around 8.8. i test every 3 days. today all of a sudden it read 8.4. is a 0.4 drop in 3 days normal? i have sps and snails, not much corraline. basically, can sps consumption alter from day to day that much or is it more likely an auto dosing malfunction?

 

[rishma]

for 2 weeks my alk was stable around 8.8. i test every 3 days. today all of a sudden it read 8.4. is a 0.4 drop in 3 days normal? i have sps and snails, not much corraline. basically, can sps consumption alter from day to day that much or is it more likely an auto dosing malfunction?

After months of extremely stable alkalinity, mine dropped 0.5 in a week. I am not at all concerned but it surprised me. Interestingly, my phosphate was much higher over this period than normal. I actually know why my phosphate was higher, it was deliberate, and I wonder if this increase in consumption of alkalinity was because the corals and coralline were growing faster with more phosphate. I’m going to keep my phosphate higher to see if the corals like it.

My point is, I don’t think your change is big deal, any could be explained due to biological processes.

 

[Randy Holmes-Farley Verified Community Expert]

for 2 weeks my alk was stable around 8.8. i test every 3 days. today all of a sudden it read 8.4. is a 0.4 drop in 3 days normal? i have sps and snails, not much corraline. basically, can sps consumption alter from day to day that much or is it more likely an auto dosing malfunction?

I would not say it’s a problem and searching for an explanation may be wasted time. It may just be testing variability.