Lowering high Alkalinity when mixing new batch of Instant Ocean

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Rst

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Every 2 weeks I mix up a new batch 66L of new salt water to attain 1.026SG & 75degrees using RO water (0 tds) and Instant Ocean (purple pails). The result is always a dKH of 11.9.

Since my desired dKH is 8.2, I have been using 31.45% Muriatic Acid, then adding 30 ml of this acid to 66L of the NSW necessary to drop the dKH from 11.9 to 8.2 as per the Reef Chemical Calculators given in this forum.

Is there something wrong with these tables, since even when I add 5 times this amount of acid (150ml), the dKH only drops to around 9 dKH?
 
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Every 2 weeks I mix up a new batch 66L of new salt water to attain 1.026SG & 75degrees using RO water (0 tds) and Instant Ocean (purple pails). The result is always a dKH of 11.9.

Since my desired dKH is 8.2, I have been using 31.45% Muriatic Acid, then adding 30 ml of this acid to 66L of the NSW necessary to drop the dKH from 11.9 to 8.2 as per the Reef Chemical Calculators given in this forum.

Is there something wrong with these tables, since even when I add 5 times this amount of acid (150ml), the dKH only drops to around 9 dKH?
Ok, I see by the lack of response I asked the wrong question. I fully assume that the chemical calculators are correct. What I should have asked is what could be causing this unexpected result and what can one check or do to obtain the desired lowering of the dKH?
Thanks
 

fcmatt

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Let me check my notes but 11.9 is silly high. That just seems wrong. Are you testing after letting it sit for at least a few hours with a pump mixing it?

Purple pail is regular io...
 
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The Aquatic Arsenal

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IO reef crystals always mixes high on alk, calcium, and magnesium. The best advice I can give is less water changes, or less amount of water changed to keep tour parameters where you want them.
 

fcmatt

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How do you calibrate your refractometer to make sure you are at 1.026?

Are you testing the fresh mix right away? How long do you wait to test? Do you have good flow in the bucket and the ability for it to aerate a bit?

Please let us know.
 
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EMeyer

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This doesn't match my results. I use 20 ml HCl in 40 gal of IO to reach 7 dKh. Something is off, have you double checked dKH?
 

gregzz4

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If you want to lower your Alk in a batch of freshly mixed SW using Muriatic Acid, use the following formula with care

Yes, you just add the acid. Be very careful with straight muriatic acid. It can easily burn you, especially your eyes.
The "acidity" (that being essentially negative alkalinity) of muriatic acid straight from the bottle is about 11,000 meq/L.
So adding 1/11,000 of the water volume of this acid will drop alkalinity by 1 meq/l (2.8 dKH).
You want a drop of 13-7 = 6 dKH, or 2.1 times that amount, so you'd add 1/5,140th of the water volume.
13 gallons ~ 49 L
1/5140 of 49 L = 9.53 mL
So I'd add 5 ml and stir well for a few minutes and see what alkalinity you get. Then dose again assuming it seems on the right track.
You'll need to aerate well after adding the acid to blow off the excess CO2 and bring up the pH.
(((A)*3.785)/(11000/((B-C)/2.8)))*1000
 
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gregzz4

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A is the amount of water you need to affect. IE your new Saltwater.
B is the Alk reading you achieved from your test kit of your new Saltwater.
C is the Alk reading you achieved from your test kit of the water you will be adding this newly mixed saltwater to, or the Alk reading you want to match.


Hope that helps !!
 
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gregzz4

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This was my original write-up

Yes, I wrote this, but you are responsible for whatever you learn from it.

Formula for lowering Alk using Muriatic Acid
Muriatic Acid is an impure form of Hydrochloric Acid. I'd recommend against using it on a regular basis to adjust your Alk levels, but sometimes you get those bad buckets of salt, so ... let's use some

If you want to skip all the links, disclaimers etc, skip to the bottom for the guts of the post.
But you've been warned about the uses of this stuff


DO NOT ADD ANY MURIATIC ACID DIRECTLY TO A SYSTEM CONTAINING LIFE
Also, do not add any MA to water you're about to use without first checking the pH after.
The effect of a significant drop in pH will most suredly kill most or all life in short order !!!
It can take many hours for the pH of water dosed with MA to come back up to acceptable levels, so use it with some smarts.

Using it comes with some responsibilities;
10 Muriatic Acid Safety Tips

Muriatic acid is readily available to most of us, but has impurities in it that Hydrochloric doesn't. Too bad for most of us. I'd rather use the purer form.

Regardless, I took some time to decipher a post by Randy Holmes-Farley to come to my final numbers.
You are welcome to check my math by visiting the post I based it on here
His is post #3

An article he authored is Chemistry And The Aquarium: Solutions To pH

And some more reading about the whole subject is available High pH: Causes and Cures

I completely agree with his thoughts on the long-term use of such a drastic measure, but when it applies to a bad bucket of salt used for water changes and such, I feel we can safely use the acid to adjust the Alk level in said water to match, or come close to, the water we are adding it to.
Just be sure it's well aerated after the addition of acid, and before adding the water to any system containing life

Another consideration is the amount of Calcium Chloride that will become available after the Alk is dropped. This is something I haven't tested yet, but will do so in the next week as I'm due for a WC.

And one more thing;
Lets make sure that you don't take anything I'm writing now as gospel. I've been known to make mathematical mistakes before, and haven't had time to test this formula in the real world !!!!!
As I stated above, I'll test it next week when I perform my next WC and report my findings.

So, lets get on with it.
From what I can calculate, based on what Randy states, it only takes 0.12287 ml of muriatic acid, or 0.123ml, or basically less than you can measure, to drop 1 gallon of saltwater by 1dKH ...
Absorb that for a second ...

To use 1ml of Muriatic Acid to safely drop the alk in any volume of saltwater, as near as I can calculate, it will drop the dKH of 8 gallons <> by 1 point.
So, lets be careful kids, this stuff is potent.

Here's my formula; I'm kinda proud of it, so don't bash me unless you find a significant error. After all, I did figure it out and post it when no one else has yet ...


(((A)*3.785)/(11000/((B-C)/2.8)))*1000

That's it. Pretty simple, huh ?

I'd recommend, because of the complexity of the formula, that you copy/paste it into a Google search.
Then change the letters to reflect your numbers and hit enter.
And be VERY careful not to change any of the other parameters while doing so !!!! Even the loss of a ( or a - will throw the formula into space !!!

I will not be held responsible for whatever amount you dose of MA to your water, but you're more than welcome to PM me if you are concerned about the final # you've come up with. I'll gladly check it against my block-head and let you know if it's correct or not.

OK, I'll elaborate

A is the amount of water you need to affect. IE your new Saltwater.
B is the Alk reading you achieved from your test kit of your new Saltwater.
C is the Alk reading you achieved from your test kit of the water you will be adding this newly mixed saltwater to, or the Alk reading you want to match.

Be very careful when entering the numbers into the formula !!!!
I hope I'm making this clear enough as dosing Muriatic Acid is very, very something ...


Again, it only takes 1ml of MA to drop 8+ GALLONS of water by 1dKH

Play safe kids, and have fun.
Oh, don't forget to check your Ca levels after the pH has come back up as it's likely your Calcium Chloride levels have risen, but I think I mentioned that above.
 
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awais98

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Every 2 weeks I mix up a new batch 66L of new salt water to attain 1.026SG & 75degrees using RO water (0 tds) and Instant Ocean (purple pails). The result is always a dKH of 11.9.

Since my desired dKH is 8.2, I have been using 31.45% Muriatic Acid, then adding 30 ml of this acid to 66L of the NSW necessary to drop the dKH from 11.9 to 8.2 as per the Reef Chemical Calculators given in this forum.

Is there something wrong with these tables, since even when I add 5 times this amount of acid (150ml), the dKH only drops to around 9 dKH?
I’m not sure if the purple pails of IO is actually 11+ dkh.
But I do know the reef crystals orange pails are 11-12.

I use purple pails the regular IO all the time and I never get fresh mixed water more that 8-9.
 

gregzz4

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I’m not sure if the purple pails of IO is actually 11+ dkh.
But I do know the reef crystals orange pails are 11-12.

I use purple pails the regular IO all the time and I never get fresh mixed water more that 8-9.
My IO readings over the last 6+ years averages out to 10.5 dKh over 40 buckets

I've kept a spreadsheet if you'd like to see it

Could be different for me here in Canada but it's what I get out of my buckets
 

homer1475

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Not sure I understand the complex math up there, nut the simple formula I found online and have used for years is as follows(of course this could be the same, but what was posted above is kind of hard to follow)....

Water volume x DKH drop x .123 = addition of acid to water in ML.

Or say you have 25G of water and need a 2DKH drop in alk

25 x 2 x .123 = 6.15ML of acid.

Not do not add this to any tank with life in it, and if your adding to a bucket of NSW, make sure you aireate it for about 24 hours prior to using(causes a huge drop in PH until fully mixed and the PH is brought back up to normal).
 
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Thanks everyone for all your replies. But my problem is not in determining the right dosage but rather the problem is WHY do I need to use over 5x known & accepted level of acid, and even when using WAY more acid, my dKH still won’t drop as needed? At start, I mixed fresh salt in 66L of RO until salt was 1.026SG. Temp was 75 deg and starting dKH was 11.9. A strong pump kept the water mixing while adding 30ml of acid. Then 24hours later, retested dKH at 11. with this much acid, the dKH should have dropped to the desired 8.3 not 11? Thereafter and over many days I kept adding more and more acid (30ml more every 12hrs) but dKH level only dropped by small amounts each time I retested. Even after adding 150ml of acid, the dKH only dropped to 8.8. This was 5x more acid than the known accepted dosage that should have easily dropped the dKH way below 8.3 but even at 5x more acid, the drop was still insufficient.

So I am baffled as to what can/should I do to get the desired drop? I guessing this has something to do with chemistry or maybe something else like not air rating the water(only strong pump mixing)? Has anybody seen this problem before and is there a fix?

Thanks all for taking your time to try and help.
 

melanotaenia

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Maybe a little off-topic, but why not just use a salt that has a more acceptable DKH for the level you desire? Seems like a lot of work to lower when you can get a different mix with an appropriate DKH for your reef.
 

madweazl

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I only need 4.5ml of low fume muriatic acid (around 15% IIRC) per 5 gallons to drop freshly mixed Instant Ocean to 7-7.5 dKh (typically mixes around 10.7 for me) ; about 15.5ml to match what you're trying to mix up.
 

dragon99

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Did you double check your muriatic acid for strength and to make sure it's not labeled "lower fumes"? Maybe you aren't using the full 31.5% acid.

Otherwise is doesn't make sense that you would adding that much acid. If I added that much acid to my IO salt mix it would be 0dKH.
 
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Melanotaenia: This would be ideal, but finding a salt with this low dKH is rare, almost all salts mix to high alkalinity. From my search only one expensive German salt(Tropic Marin) reaches down to 8

Madweazi: That,s my point, 150ml is crazy!

dragon99: Label says “MURIATIC ACID 20deg Baum commerial (31.45%) Cleaning - Etching - De-Scaling”
It doesn’t mention low fumes. Yes 150ml is crazy!
 
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