Lower Alkalinity

[Tombones]

I want to make a 20 gallon water change with tropic marin salt which has alkalinity of 8.15 and I want to lower it with muriatic acid to 7 DKH. Can anyone help me calculate how much acid to add.
Thanks

 

[landlubber]

Here is a little formula I keep in the notes on my phone.

How to mix muriatic acid:

1. dKH of your salt mix
- Tank dKH
——————
= “X”

2. “X” multiplied by # of gallons being prepared. Then multiply by .123

= mL’s of acid

so as an example:

my salt mix tests out at 10.2 dKH and my tank water is at 8.32 dKH so I subtract the 2 numbers which gives me 1.88. Today I prepared 15 gallons of new saltwater so I'm going to multiply 15 and the difference we found in dKH (1.88) which gives me 28.2. Finally multiply the 28.2 we got by .123 which is 3.4686.
what this means is to adjust my alkalinity from 10.2 down to 8.32 I am going to have to add. roughly 3.47mL of Muriatic acid.
I recommend getting ppe (glasses, gloves) a decent pipette to draw the muriatic acid and using a graduated cylinder as you're going to want to use exact measurements. Once added, I usually mix for at least 12 hours to allow pH to stabilize. After that it should be its good to be used for your water change.

I checked yours out and it calculates out to 2.829 (roughly 2.8mL of acid)

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, you can use muriatic acid or sodium bisulfate. here are some threads:

Sodium Bisulfate to Reduce Alkalinity in New Salt Water or in Display Tanks
https://www.reef2reef.com/threads/s...in-new-salt-water-or-in-display-tanks.362825/

1.2 grams per 10 Liters, drops alkalinity by 2.8 dKH.
1 level dry teaspoon of sodium bisulfate added per 100 L of tank water will drop the alkalinity by about 1.7 dKH.
Dissolve it in fresh water before adding it slowly to a high flow area.

Muriatic Acid
https://www.reef2reef.com/threads/reducing-alkalinity.339109/#post-4214464

 

[madweazl]

...

I checked yours out and it calculates out to 3.936 (roughly 3.95mL of acid)

I think it's 2.83ml by the formula you posted.

 

[landlubber]

I think it's 2.83ml by the formula you posted.

ouch. don't ask me to do your taxes on a Friday morning is the morale of this story lol. thanks for catching my mistake!

 

[madweazl]

Assuming I did the math correctly, the formula doesn't work out for my setup. I use 3ml in a 5g bucket to drop Instant Ocean from approx 10.8 to 7.2; the formula posted would suggest using 2.15ml. With that said, I didnt measure exactly 5g and perhaps the muriatic acid used makes a difference; I guess the take-away is to test it after you've added it.

 

[phlibbyreefer]

what wrong with 8.15 dkh? why would you want to lower it? My tank dkh is 9.2 currently.

 

[landlubber]

Assuming I did the math correctly, the formula doesn't work out for my setup. I use 3ml in a 5g bucket to drop Instant Ocean from approx 10.8 to 7.2; the formula posted would suggest using 2.15ml. With that said, I didnt measure exactly 5g and perhaps the muriatic acid used makes a difference; I guess the take-away is to test it after you've added it.

for me the math comes out to 2.21mL which is more or less going to give the same result anyway.
in my experience, even if the numbers are slightly off the extra .8mL of muriatic you added to the water change water above what the calculation recommends doesn't disrupt the tank parameters much once added to the system. my 10% water change is 15 gallons so I'd have to miss by several mL's to cause a noticeable dKH drop 150 gallons of water.

 

[MTBake]

Assuming I did the math correctly, the formula doesn't work out for my setup. I use 3ml in a 5g bucket to drop Instant Ocean from approx 10.8 to 7.2; the formula posted would suggest using 2.15ml. With that said, I didnt measure exactly 5g and perhaps the muriatic acid used makes a difference; I guess the take-away is to test it after you've added it.

The formula was off for me as well. I've been adding 3.2ml of muriatic acid to drive my dkh down from 9.4 to 6.0 in a 5 gallon bucket. I'm lowering my tank dkh by doing water changes. I use the low odor muriatic acid. I've read that it is diluted and this could be causing the error in the math.

 

[chipmunkofdoom2]

what wrong with 8.15 dkh? why would you want to lower it? My tank dkh is 9.2 currently.

Agreed. Having lower alkalinity is desirable under certain circumstances, but 8.15 dKh typically is sufficiently low.

Why do you want to get it to 7.0 dKh?

 

[landlubber]

I've read that it is diluted and this could be causing the error in the math.

never really thought about that but it makes total sense.

 

[Jeremy Luke]

Agreed. Having lower alkalinity is desirable under certain circumstances, but 8.15 dKh typically is sufficiently low.

Why do you want to get it to 7.0 dKh?

Certainly nothing wrong with shooting for a low dKh. I recently lowered mine to 7.5 from 8.5 and I'm seeing better coloration. I'm not an expert but Boomcorals keeps his 6.5-7.5. He prefers the lower Ph and has stated he gets his best coloration when it's lower.

 

[chipmunkofdoom2]

Certainly nothing wrong with shooting for a low dKh. I recently lowered mine to 7.5 from 8.5 and I'm seeing better coloration. I'm not an expert but Boomcorals keeps his 6.5-7.5. He prefers the lower Ph and has stated he gets his best coloration when it's lower.

Nothing wrong with it at all. Which is why I didn't say there was anything wrong with it. It is, however, unusual to shoot for exactly 7 dKh. Testing error could easily have you running alkalinity even lower than 7 dKh, which is lower than natural levels. Plus, coral calcification decrease as available carbonate and bicarbonate decreases because it's harder to build their skeletons.

That's not to say that corals can't or won't grow at alkalinity around 7 dKh. We just don't have any data to suggest that they grow better or faster, and all the data we have so far suggests that they grow slower.

 

[Jeremy Luke]

Nothing wrong with it at all. Which is why I didn't say there was anything wrong with it. It is, however, unusual to shoot for exactly 7 dKh. Testing error could easily have you running alkalinity even lower than 7 dKh, which is lower than natural levels. Plus, coral calcification decrease as available carbonate and bicarbonate decreases because it's harder to build their skeletons.

That's not to say that corals can't or won't grow at alkalinity around 7 dKh. We just don't have any data to suggest that they grow better or faster, and all the data we have so far suggests that they grow slower.

Understood. I personally wouldn't go to great lengths to lower the dKh in the new salt water for water change anyway. I'd get a mix that's as close as I can to the target and go with it. Of course, I typically change no more than 20% of my water at a time anyway. I'm currently using Fritz RPM Pro. It mixes at about 8.

 

[madweazl]

The formula was off for me as well. I've been adding 3.2ml of muriatic acid to drive my dkh down from 9.4 to 6.0 in a 5 gallon bucket. I'm lowering my tank dkh by doing water changes. I use the low odor muriatic acid. I've read that it is diluted and this could be causing the error in the math.

I am using Klean-Strip green and after looking at the safety sheet, it is 20% hydrochloric acid vs 31.4% for another I just looked up. Hadnt though about that.

 

[Randy Holmes-Farley Verified Community Expert]

Green and low odor muriatic is weakened and needs more.

 

[Tombones]

My tank is 100 gallons total volume and is at 7.5 DKH. Not bad but a 20% water change with a 8.15 alk ( maybe higher) and 8.6 ph could spike my low nutrient low phosphate SPS tank. I am using Tropic Marin I bought by mistake and online states alk at 9-10 DKH. I wanted the Tropic Marin Pro with lower alk.
I have had burnt tips on my arcopora corals before with higher alk. Low nutrient SPS tanks I think run better at lower alkalinity.

 

[KrisReef]

ouch. don't ask me to do your taxes on a Friday morning is the morale of this story lol. thanks for catching my mistake!

Hint#
Always test the final solution to verify the actual value achieved.