Ca(OH)2 and NaOH

[StevePhx]

I have been dosing NaOH for all the last 6 months. Mixing at 900gm per gallon.

My pH stays peaks at 8.1 with fuge and CO2 scrubber.

Added a kalk reactor in the last two days being fed through my ATO.

I’ve seen my pH climb to 8.3 already and climbing daily. My alk has stayed stable at 9.0 dkh.

The kalk reactor can’t supply all of my alk needs so I use the NaOH through Trident controlled dosing to top off what’s needed.

My question is why would I be seeing more of a pH increase with kalk versus NaOH? pH of 12 versus 14.

My thought is because of the dump of kalk added to the system at once versus the few drips of NaOH from my DoS every 10 minutes.

(I have a strong power head in the chamber I dose so the NaOH is being dissolved quickly)

 

[Randy Holmes-Farley Verified Community Expert]

The pH of the stock solution isn’t what matters for the pH rise in the tank. What matters in this case is the amount of hydroxide or alkalinity that gets into the water, and how fast.

The faster you add the hydroxide, the more the pH will rise because the tank has less time to respond by pulling in CO2 from the air, blunting the rise.

 

[Saltyanimals]

The pH of the stock solution isn’t what matters for the pH rise in the tank. What matters in this case is the amount of hydroxide or alkalinity that gets into the water, and how fast.

The faster you add the hydroxide, the more the pH will rise because the tank has less time to respond by pulling in CO2 from the air, blunting the rise.

when you say faster you add hydroxide does that mean more frequent and smaller doses?

Let’s take 24 ml daily for simple math. Would one see better ph out of 1 ml hourly. Or 0.5 ml every 30 mins?

I’m using your NaOH as we ve discussed on another thread but first time I’ve heard you phrased the faster notion. Ive considers making your recipe 1/2 strength instead so I can dose more of it per day as I’ve seen to hit my ceiling using NaOH with carx.

 

[Randy Holmes-Farley Verified Community Expert]

when you say faster you add hydroxide does that mean more frequent and smaller doses?

Let’s take 24 ml daily for simple math. Would one see better ph out of 1 ml hourly. Or 0.5 ml every 30 mins?

I’m using your NaOH as we ve discussed on another thread but first time I’ve heard you phrased the faster notion. Ive considers making your recipe 1/2 strength instead so I can dose more of it per day as I’ve seen to hit my ceiling using NaOH with carx.

What I meant was the faster you add the same amount of hydroxide, the higher the pH rise. At time zero, add 1 dKH of hydroxide in 5 min, you get a certain boost. If instead, at time zero you add 1 dKH of hydroxide spread over 10 hours, the pH never gets as high. BUT, at time = 10 h, the pH will be a little higher in the second case.

"Let’s take 24 ml daily for simple math. Would one see better ph out of 1 ml hourly. Or 0.5 ml every 30 mins?"

I doubt you will notice a difference between those.

How does making it half strength allow you to dose more? (it doesn't)