Using muriatic acid to combat rising alk

[Gribbles]

Hello, I have some questions I was hoping to get input on.

My alkalinity rises each day, about .2 dkh. To combat this, I have been dilluting muriatic acid with rodi water and dosing that daily. It's quite scientific and precise I assure you. I do not let it off-gas or aerate it by any means. I want to better this aspect of my reef keeping.

I'm mostly confident I know why my alk increases (I'm not explicitly dosing it...), but this thread is more about application rather than diagnosis.

What/when/how would be the best mechanism for doing this?
Would it be better if I mixed it into my water change water instead?
Does it need to off-gas for some time?
Is there a scenario where I can pull this off with a dosing pump?

 

[Miami Reef]

The Ways Alkalinity can Accumulate in a Reef Tank

The Ways Alkalinity can Accumulate in a Reef Tank @Miami Reef "Why is my alkalinity rising?" is a seemingly simple question that consistently pops up in the chemistry section of Reef2Reef. However, it is a complex question since there are...

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Dosing acid into a tank is not a good idea long-term. It’s best practice to solve the root of the problem.

 

[Miami Reef]

Acid reacts with alkalinity to form CO2 which lowers pH. You need to heavily aerate this gas from the aquarium. You can’t off-gas it prior to adding the acid to the tank.

It can substantially lower the pH of your aquarium. Too low of pH can start to dissolve coral skeletons.

 

[Miami Reef]

Would it be better if I mixed it into my water change water instead?

Yes. You can reduce the alkalinity in the water change, and heavily aerate the water about 24 hours prior to using it. That is fine.

 

[Gribbles]

Thank you, I appreciate your response but please read my post in full, I asked for application. I understand ph will drop and I am monitoring it. This is a short term solution while I sort out the long term.

 

[Gribbles]

You can’t off-gas it prior to adding the acid to the tank.

Huh? I'm pretty positive I can make a solution of water + muriatic acid (HCl) and aerate that to off-gas it before adding to the aquarium.... Am I wrong?

 

[Miami Reef]

Huh? I'm pretty positive I can make a solution of water + muriatic acid (HCl) and aerate that to off-gas it before adding to the aquarium.... Am I wrong?

If you are able to off-gas the acid, then you won’t lower the alkalinity.

Alkalinity reacts with acid to form CO2, which lowers the pH. If you want to lower the alkalinity in the tank with acid, lower pH will always be the end result until you aerate the water.

 

[Randy Holmes-Farley Verified Community Expert]

Huh? I'm pretty positive I can make a solution of water + muriatic acid (HCl) and aerate that to off-gas it before adding to the aquarium.... Am I wrong?

There is nothing to off gas and no need or benefit to aerating it.

 

[Randy Holmes-Farley Verified Community Expert]

Miami has given good advice. I’ll just add that If you have pH under basically under control in the tank, then adding a little acid each day is ok. 0.2 dKH is not much, and you can spread that out during peak pH times if you want to further minimize the drop. In general, this addition will be ok.

Most people looking to drop alk are looking at much bigger drops, so that is where the advice to not do it in the tank really kicks in.

 

[Gribbles]

Something doesn't feel right about this. Perhaps I'm not getting it or I'm not communicating my question well

For now I think my best choice would be to add the acid after I mix my water change water that I use in an AWC. Using new water that has a rather low alk might solve my issue.

I fully expect as my tank continues to mature that my alk consumption will start climbing.

 

[Randy Holmes-Farley Verified Community Expert]

Something doesn't feel right about this. Perhaps I'm not getting it or I'm not communicating my question well

For now I think my best choice would be to add the acid after I mix my water change water that I use in an AWC. Using new water that has a rather low alk might solve my issue.

I fully expect as my tank continues to mature that my alk consumption will start climbing.

Yes, that will certainly work. How often do you plan to do water changes, and of what size? If you need to drop 1.4 dKH per week, that will take substantial changes.

20% per week with water that is 7 dKH lower than the tank will do it, but realistically it will take more that is closer to the tank level.

 

[Gribbles]

I change 2 gallons per night in a ~90 gallon system

Alk of water change water currently is around 8. Tank is about 10 right now

My understanding is the HCl eventually produces excess H+ ions, lowering the ph, but how is that only temporary?

Edit: it reacts with the (bi)carbonates

 

[Randy Holmes-Farley Verified Community Expert]

I change 2 gallons per night in a ~90 gallon system

Alk of water change water currently is around 8. Tank is about 10 right now

My understanding is the HCl eventually produces excess H+ ions, lowering the ph, but how is that only temporary?

Edit: it reacts with the (bi)carbonates

Not sure what exactly you are asking, but the alk depletion is not temporary.

 

[Randy Holmes-Farley Verified Community Expert]

If you used zero alk seawater, that 2% changed daily would drop alk by 0.2 dKH. But zero alk is tricky and I suggest you’d want to change more.

 

[Gribbles]

Not sure what exactly you are asking, but the alk depletion is not temporary.

The ph drop is what I was referring to

Fwiw, I'm ok with a small addition nightly (it's what I've been doing for a little while now). Just trying to understand better so I learn

 

[Randy Holmes-Farley Verified Community Expert]

The ph drop is what I was referring to

Fwiw, I'm ok with a small addition nightly (it's what I've been doing for a little while now). Just trying to understand better so I learn

The pH drop in seawater is temporary due to blowing off of excess CO2 from the H+ combining with bicarbonate

 

[Gribbles]

The pH drop in seawater is temporary due to blowing off of excess CO2 from the H+ combining with bicarbonate

Ok, makes sense and that's what I'm seeing when I dose the acid. In rodi, then, there would be no reaction that forms the CO2 because no bicarbonate exists in that system to react with.

So adding the muriatic acid to the mixing reservoir would be ideal then, in my scenario. I could aerate for a little bit until the pH returns to normal.

You mentioned zero alk is tricky, could you summarize briefly as to why?
Any concerns you can foresee with my proposed process? Any harm to a mixing pump or air stone, etc? Further changes to water chemistry we didn't discuss here?

I have a better overall understanding, thank you and @Miami Reef

 

[Troylee]

Hello, I have some questions I was hoping to get input on.

My alkalinity rises each day, about .2 dkh. To combat this, I have been dilluting muriatic acid with rodi water and dosing that daily. It's quite scientific and precise I assure you. I do not let it off-gas or aerate it by any means. I want to better this aspect of my reef keeping.

I'm mostly confident I know why my alk increases (I'm not explicitly dosing it...), but this thread is more about application rather than diagnosis.

What/when/how would be the best mechanism for doing this?
Would it be better if I mixed it into my water change water instead?
Does it need to off-gas for some time?
Is there a scenario where I can pull this off with a dosing pump?

I know you don’t wanna talk about it but can I ask why it’s rising if you’re not dosing it? I’m confused..

 

[Randy Holmes-Farley Verified Community Expert]

The pH won’t return to normal, but at best will be a bit lower than before the addition.

Zero alk seawater is a tricky balance and will have pH around 6-7 even after aeration. Before aeration it will be just over 4. That pH won’t have a strong imPact on tank pH if aerated, but a little too much acid will send the pH below 4 and that won’t come up with aeration.

 

[Gribbles]

I know you don’t wanna talk about it but can I ask why it’s rising if you’re not dosing it? I’m confused..

I've received lots of good input about the application process, so I think I'm good there.

As for why, you're correct in that I'm not explicitly dosing any 2 part, all-for-reef or anything that directly increases alk (as far as I'm aware). The only thing I currently dose (other than this acid) is TM's Bacto Balance. Unless I'm mistaken, it's a form of carbon dosing with added nitrate and phosphate to keep those levels detectable. There's some relationship between nitrate dosing/consumption and alk. I'd need to go back and find some notes to find the specifics. It's another thread I've posted here somewhere

So, my evidence gathered is such:

1. Carbon dose with added nitrates
2. Feed incredibly heavy
3. High-ish bioload
4. Corals are still frags
5. Little coralline algae yet
6. Nitrates have stayed consistently around 10ppm for several months now

My theory is then:
My alk consumption is minimal at best from coral growth
The carbon dosing and removal of nitrates results in a minimal net gain of alk

Having said all of that.. the corals are growing and coralline algae is appearing throughout the tank. And the coral are looking great, as far as my standards go I suspect my alk consumption from corals will steadily increase with time.

Does my theory sound reasonable, or do you have other suggestions?