BRS two part question

[Longnose Hawkfish]

Hello, I had a few questions about brs two part dosing. To start it off I checked my levels in my tank which has about 100g of water in it. This is what I got

Calc. 390-400 ppm (Red Sea and API)
Alk. 6.5 dKH (Red Sea) 7 dKH (API)
Mag. 1320 ppm (Red Sea)

Well I wanted to raise my number to:
Calc. 420 ppm
Alk. 9dKH
Mag. Stay the same

I used the reef chem calculator and made sure everything was right and put in my numbers.
To get calc up i needed 255.8 ml calcium chloride
To get alk up I needed 178.5 ml of soda ash

So I split the dose up into two different doses for calcium and four doses for alk. I split this up over 48 hours.

Now I went to recheck numbers and alk only went up to 8 and calcium is at 400. I am wondering why there is almost no change in my numbers? I know nothing is wrong with 8 and 400 but I would prefer to keep it a tad but higher. Is there any reason why the calc would stay at 400? Should I add more solution? Thanks!

 

[Randy Holmes-Farley Verified Community Expert]

First, many aquarists overestimate the accuracy of their test kits. Small changes should be viewed with a very skeptical eye, and longer trends, especially in calcium, are more useful.

Second, there could have been deposition of calcium carbonate during this period, reducing the values of both.

You also had to estimate the water volume, which may be off.

From here, I'd stick with equal parts dosing for a while and add some of each every day to maintain alkalinity. Calcium will likely follow along just fine unless water changes drive it up or down.