NaOH for pH

[LobsterOfJustice]

I’m considering trying NaOH for a pH boost. My main questions are:

1. Does NaOH affect alkalinity? And if so, how much?
2. Is NaOH stronger than kalk at boosting pH? ie, Can I expect to use a much smaller volume of NaOH to maintain a given pH than the equivalent volume of kalk?


The details:
My pH runs 7.7 - 7.9 even when pumping outside air into the skimmer (this actually had no effect). The indoor portion of my system (the DT) is built in wall and closed into cabinetry and the rest of the system is in the garage (ie not a living space where people are filling with CO2). So I don’t think atmospheric CO2 is the right rabbit hole to go down here. I am quite happy with my use of two part and I’m able to keep alkalinity super stable which is important to me. I’m currently dabbling a little in kalk in an effort to raise and/or stabilize the pH but I’m seeing much more of an effect on alk than pH which is not what I want. Additionally I obviously would like to boost pH at night however my system uses only 20% of the per hour alk demand between 12-6 AM as it does during daytime so any significant amount of kalk dosed overnight leads to alkalinity instability. This is why I’m specifically interested in trying NaOH.

 

[KStatefan]

Randy has a thread on using Sodium Hydroxide for dosing.

New DIY Two Part Recipes with Higher pH Boost

Here's a first crack at what may end up being multiple possible recipes for a DIY two part that either has a higher pH or can be made more concentrated than traditional two part recipes. This one has about twice the pH raising effect compared to a carbonate based two part, per unit of...

www.reef2reef.com

 

[Randy Holmes-Farley]

Certainly, hydroxide in any additive is an alk supplement, as in my diy two part, kalkwasser, or the false claimed pH boost plus from Brightwell,

 

[Randy Holmes-Farley]

The hydroxide boosts pH about twice as much as carbonate per unit of alk added. The boost is identical for any source of hydroxide, such as NaOH or kalkwasser per unit of alk added.

 

[Corolling]

I've been dosing NaOH for about 6-8 weeks or so. I've been dosing straight into my return section. I have a mp40 in there, and the wetside fell, and it wasn't receiving much agitation. I have a basement sump, so i don't see it every day. One evening I went down into the basement and found a ton of undissolved NaOH or that looked like snow on the bottom of the sump, so I vacuumed it out, and put an additional wavemaker in the return chamber with the mp40. So far so good. I do get a big bump of ph from it, as well as an increase ALK. So far so good. I've had issues with calcium hydroxide seizing my wavemakers and return pumps. I hope i don't see the same with NaOH.

As everyone else will say, please adhere to safety while working with it, as well as having the proper dosing hoses.

BTW, i found that my skimmer has been going crazy since dosing NaOH. Massive bubbles, all the time. I can't keep a constant setting on my skimmer to not overflow. So be mindful of that. It could be something unrelated.

 

[LobsterOfJustice]

As everyone else will say, please adhere to safety while working with it, as well as having the proper dosing hoses.

If I make an NaOH solution roughly 3-4x as concentrated as the DIY 2-part recipe, is it compatible with:

1. Silicone tubing
2. Santoprene tubing (as found in BRS dosing pump)
3. Acrylic (dosing container)

 

[Randy Holmes-Farley]

If I make an NaOH solution roughly 3-4x as concentrated as the DIY 2-part recipe, is it compatible with:

1. Silicone tubing
2. Santoprene tubing (as found in BRS dosing pump)
3. Acrylic (dosing container)

Imo, I’d make it the same potency unless there’s a strong reason to make it more potent. The risks of local precipitation rise as the concentration rises.

Those materials are ok in NaOH solutions.

 

[LobsterOfJustice]

Imo, I’d make it the same potency unless there’s a strong reason to make it more potent. The risks of local precipitation rise as the concentration rises.

Those materials are ok in NaOH solutions.

Ok thanks. I just have a big tank with lots of big corals so I go through a lot of 2 part and I don’t want to be refilling it every week lol. I just checked back on another thread where I asked for you help on a cost comparison and you calculated that my current DIY recipe is roughly 1.5x strength so I might target that just to keep consistent and facilitate dosing changeover.

 

[LobsterOfJustice]

The hydroxide boosts pH about twice as much as carbonate per unit of alk added. The boost is identical for any source of hydroxide, such as NaOH or kalkwasser per unit of alk added.

Is there a delay in the process that turns NaOH into measurable alkalinity?

I adjust my dosing volume throughout the day to try and keep alk as stable as possible. My systems demand between midnight and 6am is very low (previously with sodium carbonate I was dosing about 1/4 the amount hourly between midnight and 6am compared to the rest of the day). With the hydroxide i have lowered this dosing period to zero - no dosing at all between midnight and 6am - but I am still consistently seeing alk jump by about 0.1 between these two intervals.

 

[Randy Holmes-Farley]

No, hydroxide can be measured with an alk kit while still in the dosing solution, but in reality, when added to seawater it instantly combines with bicarbonate and carbonic acid to form carbonate and bicarbonate (as well as some other reactions that boost alk).

I’m not sure what the issue is for that small alk change, but there are a variety of minor processes that add and remove alk that might cause it. It might also be an error associated with the test that relates to the starting pH and how that can impact the measured alk.