High Alkalinity help

Tautog · May 1, 2019

I’m using Reef Crystals for the past 4 yrs, but recently a new batch of WC water had a Alkalinity of 14 dKH on both Hanna and Rea Sea tests. These tests were done 3 days after mixing, and aeration. I mixed the salt into a 50 gal barrel of R/O in 4 stages( full bag from 200 gal box ), until fully dissolved. I use a wooden paddle. Instant Ocean was no help.
1- What is the best method to reduce the Alkalinity for a WC?
2- Are my mixing methods wrong? The water is heated to 76 degrees before mixing.
3- How much Vinegar could I use, or have to use to reduce the Alkalinity to at least 10 dKH?
4- I have diluted with R/O, but only raised the salinity with little reduction on the Alkalinity.
What’s the solution? I have not changed my mixing or added anything new.
I have had this issue with the past 4 mixes, and 3 different boxes. I’m stumped!

laverda · May 1, 2019

You want to use a little muratic acid to drop the ALK of you NSW. There is a thread in this forum about it.

Tautog · May 3, 2019

laverda said:
You want to use a little muratic acid to drop the ALK of you NSW. There is a thread in this forum about it.

Thanks for your reply, I was waiting for a reply from Randy. I couldn’t find the thread. I was asking how much acid would be needed to lower the Alkalinity from 14 to 10 dKH, based on 45 gallons of water? Adding a little wouldn’t make a dent , but thanks anyway.
By adding 300 ml of Vinegar to 45 gal. of NSW, the Alkalinity dropped to 11.5, fwiw. Close enough.

Randy Holmes-Farley · May 4, 2019

Reef Crystals is a high alk mix, and while 14 dKH is a bit higher than normal for it, with the potential error in alk testing and salinity testing, and even inhomogeneity within a bucket, it's not particularly unusual.

here's a thread where I work through acid dosing (preferably outside the tank in new salt water):

https://www.reef2reef.com/threads/muriatic-acid.325918/

one section:

Normal muriatic acid is about 35% HCl. Check the label and see what it is.

For normal muriatic acid,

Be very careful with straight muriatic acid. It can easily burn you, especially your eyes.

The "acidity" (that being essentially negative alkalinity) of full strength 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).

That sounds like a good dose.

You'll need to aerate well after adding the acid to blow off the excess CO2 and bring up the pH.