Alkalinity Reduction

[kevin_e]

Hi everyone,

I am wanting to drop my alkalinity in my aquarium over time through water changes. My tank concentration is 10.3 dKH and the water I am using to do water changes with it 7.89 per an ICP analysis.

My tank is 50 gallons, my water changes are 5 gallons. How many water changes would it take to get to a concentration of 8 dKH?

 

[Randy Holmes-Farley Verified Community Expert]

8.00 dKH at 29 changes. lol

My suggestion is to lower the alk more in the new salt water if you want to bring it down only by water changes. Muriatic acid or sodium bisulfate in the new salt water, followed by aeration to raise pH back up work well for that.

FWIW, ICP doesn't measure alkalinity, so the company just ran a normal alk test on the water.

 

[kevin_e]

Thanks Randy. Is there another way that you would suggest bringing it down besides water changes? Naturally dropping it won't happen quickly. Not nearly enough consumption.

Do you suggest one product over another? I'm assuming I can Google a calculator for dosing my new salt water to target a specific alk. Any suggestion on what dKH I should drop the new salt water to? Say I drop it to 4 would that cut my water changes from 29 to 15ish?

 

[kevin_e]

8.00 dKH at 29 changes. lol

My suggestion is to lower the alk more in the new salt water if you want to bring it down only by water changes. Muriatic acid or sodium bisulfate in the new salt water, followed by aeration to raise pH back up work well for that.

FWIW, ICP doesn't measure alkalinity, so the company just ran a normal alk test on the water.

Search results for: '' - Bulk Reef Supply

Bulk Reef Supply - Saltwater Aquarium Supplies for Reef Tanks

www.marinedepot.com

I found an old thread of yours referencing this product, which is sodium bifsulfate. I think this is the route I will go. I will need to do a lot of research, because I don't want to drop alk. by more than 0.5meq/lt or 1.4 dKH per day, which is what BRS recommends when RAISING alk. Seems practical to heed that same advice when dropping alk.


I am just unsure how far I should drop the alk. in my bucket of new saltwater to achieve a drop of 1.4 dKH in my tank in a 5 gallon water change, assuming that is even possible using 5 gallons.

Sodium Bisulfate to Reduce Alkalinity in New Salt Water or in Display Tanks

I just want to record these calculations in their own thread to refer back to in other threads. When alkalinity is too high in new salt water or in a display tank, acid can be used to lower the alkalinity. You can easily use muriatic acid (hydrochloric acid), or sodium bifulfate (e.g...

www.reef2reef.com

 

[Randy Holmes-Farley Verified Community Expert]

I would not add it to the tank unless you do it super slowly since both it and muriatic acid drop pH a lot.

My suggestion is water changes with low or zero alk water made with these methods. That's what I was suggesting above. The low alk new salt water can be brought up in pH by aeration.

 

[homer1475]

The calc for your new mixed water is easy peasy. I use it all the time when I'm mixing water(hate how high my mix is)

Water volume X Alk drop X 0.123 = amount of acid to add in ML.

For example: 30G of water with an ALK drop of 2:

30 X 2 X 0.123 = 7.38Ml of muriatic acid. I would just use 7.4ML.

AGIN AS RANDY STATED, DO NOT PUT THIS IN YOUR TANK. IT'S ONLY FOR NEW MIXED WATER. The PH drop is significant and your NSW should be aerated for 24 hours to bring the PH back up prior to using.

 

[kevin_e]

I would not add it to the tank unless you do it super slowly since both it and muriatic acid drop pH a lot.

My suggestion is water changes with low or zero alk water made with these methods. That's what I was suggesting above. The low alk new salt water can be brought up in pH by aeration.

Great, thank you. I will try that. I wasn't sure if "0" alk was acceptable. Is there a calculator for me to gauge how replacing 5 gallons with 0 alk in a tank of 50 gallons with 10.3 alk would end up at?

 

[Randy Holmes-Farley Verified Community Expert]

Great, thank you. I will try that. I wasn't sure if "0" alk was acceptable. Is there a calculator for me to gauge how replacing 5 gallons with 0 alk in a tank of 50 gallons with 10.3 alk would end up at?

0.95 x 10.3 + 0.05 x 0 = 9.8 dKH

 

[kevin_e]

0.95 x 10.3 + 0.05 x 0 = 9.8 dKH

Thanks Randy. To get a better understanding, the 0.95 and 0.05 are percentages times the relative concentration. Wouldn't 5 gallons of 50 gallons be 0.1, not 0.05?

 

[homer1475]

Randy, how do you get 0 alk water? I realize you can add acid to get it to 0, but wouldn't that cause other elements to fall out of place?

Just curious.

 

[kevin_e]

Randy, how do you get 0 alk water? I realize you can add acid to get it to 0, but wouldn't that cause other elements to fall out of place?

Just curious.

Good question. I will say that for my case, I would only be doing 10% water changes a few times to get my alk. down in a few water changes as opposed to 29 water changes. Then I will be using a salt (Red Sea) more aligning with the alk. I want to keep my tank at (8 dKH). So this shouldn't be a long term issue in my case.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks Randy. To get a better understanding, the 0.95 and 0.05 are percentages times the relative concentration. Wouldn't 5 gallons of 50 gallons be 0.1, not 0.05?

Oh, sorry, yes.

 

[Randy Holmes-Farley Verified Community Expert]

Randy, how do you get 0 alk water? I realize you can add acid to get it to 0, but wouldn't that cause other elements to fall out of place?

Just curious.

I don't know of anything that will precipitate from 0 alk seawater. That said, don't go past zero, because then you will not be able to bring the pH back up by aeration

maybe target a low alk, not zero.

 

[homer1475]

I don't know of anything that will precipitate from 0 alk seawater. That said, don't go past zero, because then you will not be able to bring the pH back up by aeration

maybe target a low alk, not zero.

Yeah was more just a general curiosity, then any scientific data. Thanks for the clarification.

 

[kevin_e]

Oh, sorry, yes.

Thank you sir.

 

[kevin_e]

Good question. I will say that for my case, I would only be doing 10% water changes a few times to get my alk. down in a few water changes as opposed to 29 water changes. Then I will be using a salt (Red Sea) more aligning with the alk. I want to keep my tank at (8 dKH). So this shouldn't be a long term issue in my case.

Can you double check my math on dosing the Seachem product?

The bottle says 1/4 teaspoon will drop alk in 20 gallons by 0.6 dKH.

So 1/4 tsp would drop alk in 5 gallons by 2.4 dKH....and 1/4 + 1/8 teaspoon will drop alk in 5 gallons by 3.6 dKH.

If my current dKH in the 5 gallons of salt mix is 7.89 and I add 1/4 + 1/8 teaspoon on product, I should find alk in my 5 gallons to be in neighborhood of 4.29 dKH, give or take.

Doing a 5 gallon water change with 4.29 dKH in 50 gallons of water with dKH of 9.91 would yield a new dKH of 9.35.

Does that sound right?


Does that sound right?

 

[Randy Holmes-Farley Verified Community Expert]

Assuming the Seachem info is correct, that all holds together.

Remember that you will need to aerate the new water well to boost the pH back up.

 

[kevin_e]

Assuming the Seachem info is correct, that all holds together.

Remember that you will need to aerate the new water well to boost the pH back up.

Fantastic! Thanks. I just checked the pH and measured 7.69. I have a large PH in there now and windows open. I'll check again tomorrow afternoon. Plan on doing 6 water changes over 6 days, no more than 0.5 dKH change per day. Probably overly cautious, but it will give me something to do during these Covid times.

 

[kevin_e]

Just to update progress for if anyone comes across this thread and has the same issues.

My first water change mathematically targeted a tank water concentration on 161 ppm. I tested 157 ppm. The second water change targeted 153. I tested 153.

So far so good. And props to the Hanna Alk checker. Pretty much spot on.