Reducing alkalinity ?

[AB_Reefer]

Hi Randy.
I am running ULNS so keeping my Alk stable at 7 dkh. Now the issue I face is when I do water change with instant ocean salt which mixes at much higher alk and as a result I am unable to do a larger water change without significantly raising my Alk.
Is there a way to safely reduce the alk level of a freshly mixed batch of saltwater?

( unfortunately I don't have access to other salts which mix at lower alk levels )

Cheers.
Karan

 

[Cory]

Hi Randy.
I am running ULNS so keeping my Alk stable at 7 dkh. Now the issue I face is when I do water change with instant ocean salt which mixes at much higher alk and as a result I am unable to do a larger water change without significantly raising my Alk.
Is there a way to safely reduce the alk level of a freshly mixed batch of saltwater?

( unfortunately I don't have access to other salts which mix at lower alk levels )

Cheers.
Karan

You could add small amounts (drops) of muriatic acid from the hardware store.

 

[AB_Reefer]

You could add small amounts (drops) of muriatic acid from the hardware store.

Thanks @Cory ..
Will this only affect alk or any other parameters as well ?

 

[Randy Holmes-Farley Verified Community Expert]

It won't impact anything else except pH, which it lowers a lot. Aeration will slowly bring it back up.

Here's a copy and past of an old post of mine for a guy who wanted to use it to drop the alk from 13 to 7 dKH in 13 gallons of salt water.:


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 normal (not low fume type) muriatic acid straight from the bottle is about 11,000 meq/L.

So adding 1/11,000 of the water volume as 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 1/5,100th of the water volume.

13 gallons ~ 49 L

1/5100 of 49 L = 9.6 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.

 

[GainesvilleReef]

It won't impact anything else except pH, which it lowers a lot. Aeration will slowly bring it back up.

Here's a copy and past of an old post of mine for a guy who wanted to use it to drop the alk from 13 to 7 dKH in 13 gallons of salt water.:


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 normal (not low fume type) muriatic acid straight from the bottle is about 11,000 meq/L.

So adding 1/11,000 of the water volume as 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 1/5,100th of the water volume.

13 gallons ~ 49 L

1/5100 of 49 L = 9.6 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.

This is what I do and it works well.

 

[aeras1131]

Why not simple get a low alk salt like Red Sea blue bucket. Anything else is just compromising.

 

[GainesvilleReef]

Why not simple get a low alk salt like Red Sea blue bucket. Anything else is just compromising.

I agree. I use plain old IO and do not need to do this on a regular basis. But it is a useful technique if you are trying to match existing parameters like in the case of a large water change.

 

[AB_Reefer]

Why not simple get a low alk salt like Red Sea blue bucket. Anything else is just compromising.

Buying the red sea blue bucket would have been the first thing I would have done if I had the option
Reefing in Vietnam has its challenges.. supply of different varieties of salt just being 1 small aspect of it.. instant ocean and aquavitro is what all LFS are stocking these days.. no Red sea unfortunately..

 

[AB_Reefer]

It won't impact anything else except pH, which it lowers a lot. Aeration will slowly bring it back up.

Here's a copy and past of an old post of mine for a guy who wanted to use it to drop the alk from 13 to 7 dKH in 13 gallons of salt water.:


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 normal (not low fume type) muriatic acid straight from the bottle is about 11,000 meq/L.

So adding 1/11,000 of the water volume as 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 1/5,100th of the water volume.

13 gallons ~ 49 L

1/5100 of 49 L = 9.6 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.

Thanks Randy.. this is just what I needed

 

[Randy Holmes-Farley Verified Community Expert]

Thanks Randy.. this is just what I needed

You’re welcome.

Happy Reefing. [emoji3]

 

[Velcro]

I do this with my aquavitro salinity which mixes 9.5-10 dkh. If I were only doing 10% waterchanges I wouldn't bother, but I've been doing 35-40% so I use muriatic acid to drop it.

 

[madweazl]

Why not simple get a low alk salt like Red Sea blue bucket. Anything else is just compromising.

Compromising what? I'd rather save the $30.

 

[aeras1131]

@madweazl You would be working against your target params making it more difficult to maintain your reef at your target params. You never know when you are going to have to do that large water change

 

[Velcro]

@madweazl You would be working against your target params making it more difficult to maintain your reef at your target params. You never know when you are going to have to do that large water change

What? He’s talking about correcting alk in instant ocean. This is easy to do and many people practice this regularly. The rest of the IO parameters aren’t that bad. Maybe needs a bump in calcium/mag but that’s cheap and easy

 

[madweazl]

@madweazl You would be working against your target params making it more difficult to maintain your reef at your target params. You never know when you are going to have to do that large water change

Like I said, I'd rather save the $30.

 

[aeras1131]

@madweazl and I like to keep things simple *cheers*

 

[aeras1131]

simple trumps money. If I did not want to burn money, I would not have bought a reef tank. Honestly, in the grand scope of things 30 dollars is less then 2 hours of work for me. For me, it is worth the money to use the right tool for the job.

 

[Velcro]

simple trumps money. If I did not want to burn money, I would not have bought a reef tank. Honestly, in the grand scope of things 30 dollars is less then 2 hours of work for me. For me, it is worth the money to use the right tool for the job.

Why are you posting in this thread? He didn’t ask for opinions on whether to adjust alk.

 

[Randy Holmes-Farley Verified Community Expert]

I can’t see how adjusting a salt mix alk is any concern or using the “wrong” tool. I never did it because I preferred the higher alk in IO, but if you don’t, lowering it doesn’t make it a bad mix.

 

[aeras1131]

Sorry I came across wrong.