Dosing kalkwasser but poor pH gains at max dose.. what gives?

[nim6us]

Like many of us I've succumb to all the buzz about pH. This week I have been transitioning over from Tropic Marin AFR to a majority kalkwasser for my dosing. As of today I reached my max dosing amount I can handle with my evaporation, roughly 2L a day of kalk. However at this dosage I've only seen a 0.1 bump in pH. I tested and the mix is potent; it's definitely raising alk/cal as I've had to dial my AFR dosing way back. The kalk solution itself is testing 12.39 pH.

I guess from everything I've been reading I was more expecting to spike my pH, that if I wasn't careful I'd see a rapid increase. To find out I'm at my max dose and only seeing a 0.1 gain is, A) disheartening but B) also makes me wonder if I'm doing something wrong.

Below are the details of my setup as well as a picture of my tank (sorry it came out so blue) to give you an idea of corals I keep. I'm looking for any advice from those with experience please.

Details

• Red Sea 425XL - Roughly 400L water volume - running for about 3 years
• Previous pH 7.9 at night to 8.1 peak during the day
• Previous dosing 35ml a day AFR
• Current dosing 2.1L of kalk and 10ml AFR
• Current pH 8.0 at night to 8.2 peak during the day
• Using Kamoer continuous duty doser to drip all day
• 0.5 dkH daily consumption
• 2L-2.25L daily evaporation
• Using Reef Factory pH probe to measure, probe was calibrated this week and confirmed readings with standards
• Kalkwasser is being stored at room temp and pH is measuring 12.39

 

[Miami Reef]

What is your alkalinity at?

A few thoughts:

1) Your tank looks phenomenal and I see growth. Not sure if chasing pH higher than 8.2 is needed if it’s working well for you.

Now, if you are just curious about why pH isn’t going higher, here’s what I think

1) Keep your alkalinity higher than 8dKH. Higher alkalinity is more buffer which means pH will be more stable and more higher. It also requires more dosing to keep higher, which means higher pH (if dosing high pH additive).

2) Switch to sodium hydroxide for all your alkalinity needs. It raises the pH the same way kalkwasser does per unit of alkalinity, but the solution can be made much, much more potent than kalkwasser, which means you can raise your alkalinity far beyond than evaporation limits.

3) Limiting aeration can actually help you raise pH when used with sodium hydroxide. It can help with kalkwasser too, but then you’ll be even more limited by evaporation with how much kalkwasser you can dose which will work against you.


However, I don’t believe making any change is necessary. Your pH is more than adequate IMO.

Link for sodium hydroxide recipe: https://www.reef2reef.com/threads/second-new-diy-two-part-recipe-with-higher-ph-boost.357080/

 

[nim6us]

@Miami Reef
To your first point, I suspect you're probably right. I'm actually happy with my tank and the growth, but as I eluded to in my first post I'm always curious to see if I can make more gains. I'm interested in kalk, I just want to make sure I'm doing it right, but if I don't hit 8.3 it's not the end of the world for me.

I believe you're also right on the money regarding alk. I usually keep my alk at 8.0 dKH and if that's a limiting factor in pH buffering, well my current results make total sense!

Finally I appreciate the tip about sodium hydroxide, I'll definitely look into that.

Your advice was bang on what I was looking for, thank you for taking the time to give me such good feedback.

 

[Miami Reef]

@Miami Reef
To your first point, I suspect you're probably right. I'm actually happy with my tank and the growth, but as I eluded to in my first post I'm always curious to see if I can make more gains. I'm interested in kalk, I just want to make sure I'm doing it right, but if I don't hit 8.3 it's not the end of the world for me.

I believe you're also right on the money regarding alk. I usually keep my alk at 8.0 dKH and if that's a limiting factor in pH buffering, well my current results make total sense!

Finally I appreciate the tip about sodium hydroxide, I'll definitely look into that.

Your advice was bang on what I was looking for, thank you for taking the time to give me such good feedback.

Perfect! I’m glad my response was helpful.

I use the sodium hydroxide myself and my pH hits 8.5 by the end of the day.

 

[Randy Holmes-Farley]

Using ANY method of raising pH (except fresh air to the room) is typically fighting against aeration at the tank top with high CO2 air. High aeration and high CO2 often wins out.

 

[nim6us]

I think this is one of the most appealing things to me about reefing. There's math, engineering, plumbing, chemistry, biology, and so many other disciplines involved in keeping a reef tank. It broadens your horizons, teaches you new skills, and rewards critical thinking. Best of all if you lean into all of it, the result is a beautiful thriving ecosystem.

This community is so valuable, having knowledgable, helpful people to guide you really enhances the journey!

 

[Rigoberto]

Perfect! I’m glad my response was helpful.

I use the sodium hydroxide myself and my pH hits 8.5 by the end of the day.

Hi Miami Reef, Sodium Hydroxide... what are you using to make an aqueous solution?.

 

[Miami Reef]

Hi Miami Reef, Sodium Hydroxide... what are you using to make an aqueous solution?.

Sodium Hydroxide - Pure - Food Grade (Caustic Soda, Lye) (2 Pound Jar) https://a.co/d/i2rT01e

 

[Rigoberto]

Using ANY method of raising pH (except fresh air to the room) is typically fighting against aeration at the tank top with high CO2 air. High aeration and high CO2 often wins out.

How about a CO2 scrubber on the intake to skimmer?

 

[trevorhiller]

Perfect! I’m glad my response was helpful.

I use the sodium hydroxide myself and my pH hits 8.5 by the end of the day.

What dosing pump do you use for the Sodium Hydroxide?

I was looking into this before and had some concerns about chewing through dosing pump tubing.

 

[Miami Reef]

What dosing pump do you use for the Sodium Hydroxide?

I was looking into this before and had some concerns about chewing through dosing pump tubing.

BRS 1.1mL pumps. It is safe with high pH. It uses Santoprene on the inside.

 

[NabberNate]

Using ANY method of raising pH (except fresh air to the room) is typically fighting against aeration at the tank top with high CO2 air. High aeration and high CO2 often wins out.

I'm one day into a kalkwasser setup and I've gone from 7.65 to 7.9 switching from baked baking soda (your recipe... much appreciated).
Is that all I should hope for then?

Not going to blow money on CO2 scrubber. Getting an external air line how thick does the line need to be and how far can it go? I'm in the a finished basement won't be easy.

 

[Jonify]

Using ANY method of raising pH (except fresh air to the room) is typically fighting against aeration at the tank top with high CO2 air. High aeration and high CO2 often wins out.

What Randy said. I’d recommend checking out your room CO2 levels for a baseline before you do anything else to chase pH. You can get an inexpensive air quality monitor from Amazon for about $100. Normal fresh air is about 400ppm CO2. IME, room CO2 levels above 700 ppm is a pH fight. Above 1000 is a losing fight. You can open or crack some windows to address that, but if you’re not able to do that, a CO2 scrubber has worked wonders for me. In my old place, where CO2 regularly hit 1200ppm (small apartment, tightly sealed, 2 humans breathing), that CO2 scrubber took me from a pH of 7.9 to 8.2. If I cracked my windows, I’d get up to 8.3. That’s how important CO2 levels are to pH. And that’s without dosing Kalk, I was using baking soda. How can humans in a space impact CO2 levels so much? We breathe out as much as 50,000 ppm CO2; so, if it builds up quicker than it’s vented out, that’s how. One other thought … if you have a well sealed home and you turn on a gas stove, that pH will drop fast as oxygen is burned and your CO2 skyrockets. I used to get very cross at my roommate for turning on the stove without opening the windows first

 

[NabberNate]

What is your alkalinity at?

A few thoughts:

1) Your tank looks phenomenal and I see growth. Not sure if chasing pH higher than 8.2 is needed if it’s working well for you.

Now, if you are just curious about why pH isn’t going higher, here’s what I think

1) Keep your alkalinity higher than 8dKH. Higher alkalinity is more buffer which means pH will be more stable and more higher. It also requires more dosing to keep higher, which means higher pH (if dosing high pH additive).

2) Switch to sodium hydroxide for all your alkalinity needs. It raises the pH the same way kalkwasser does per unit of alkalinity, but the solution can be made much, much more potent than kalkwasser, which means you can raise your alkalinity far beyond than evaporation limits.

3) Limiting aeration can actually help you raise pH when used with sodium hydroxide. It can help with kalkwasser too, but then you’ll be even more limited by evaporation with how much kalkwasser you can dose which will work against you.


However, I don’t believe making any change is necessary. Your pH is more than adequate IMO.

Link for sodium hydroxide recipe: https://www.reef2reef.com/threads/second-new-diy-two-part-recipe-with-higher-ph-boost.357080/

Can sodium Hydroxide be dosed using my existing kalkwasser reactor? I don't have enough evaporation to keep up my alk using Kalkwasser and increasing my surface water agitation drops my ph. I do have an external air line. Thanks!

 

[Randy Holmes-Farley]

I'm one day into a kalkwasser setup and I've gone from 7.65 to 7.9 switching from baked baking soda (your recipe... much appreciated).
Is that all I should hope for then?

Not going to blow money on CO2 scrubber. Getting an external air line how thick does the line need to be and how far can it go? I'm in the a finished basement won't be easy.

pH effects rarely take more than a day to establish themselves.

 

[Randy Holmes-Farley]

Can sodium Hydroxide be dosed using my existing kalkwasser reactor? I don't have enough evaporation to keep up my alk using Kalkwasser and increasing my surface water agitation drops my ph. I do have an external air line. Thanks!

Not unless the kalkwasser is well below saturation. . Addition of either hydroxide or calcium will suppress the dissolution of the calcium hydroxide.

 

[92Miata]

3) Limiting aeration can actually help you raise pH when used with sodium hydroxide. It can help with kalkwasser too, but then you’ll be even more limited by evaporation with how much kalkwasser you can dose which will work against you.

The aeration thing is really frustrating - a lot of people don't seem to realize that the primary drivers of tank pH are indoor CO2 concentration and photosynthesis in the tank. The most impactful processes in the tank drive pH up - and tons of aeration in a house with high CO2 makes things worse.

Aeration is almost never helpful with pH unless you're aerating using outside air.

 

[NabberNate]

Thanks Randy I meant to replace the Kalkwasser substrate in the stirrer with the sodium hydroxide not add them both.
I'm really struggling to figure this out and appreciate your help.

I recently have added a kalkwasser reactor which bumped me from 7.65 to 7.9 ph at a dkh of 11 (max recommended). Last night I added an external air line to my skimmer and now I'm at 8.05. I also minimized my surface water agitation this morning since it is a rimless tank with an open sump so we will see.

I have tried using a CO2 scrubber in the past and PH would be around 8.3 / 8.4 I just don't like refilling the media because when it loses potency its a big drop fast. I would have thought my external air line would be as effective as a CO2 scrubber does it just take more time? Will water changes help? I don't do the 20% a month more like 10%.

Thanks again!

 

[Randy Holmes-Farley]

Thanks Randy I meant to replace the Kalkwasser substrate in the stirrer with the sodium hydroxide not add them both.
I'm really struggling to figure this out and appreciate your help.

I recently have added a kalkwasser reactor which bumped me from 7.65 to 7.9 ph at a dkh of 11 (max recommended). Last night I added an external air line to my skimmer and now I'm at 8.05. I also minimized my surface water agitation this morning since it is a rimless tank with an open sump so we will see.

I have tried using a CO2 scrubber in the past and PH would be around 8.3 / 8.4 I just don't like refilling the media because when it loses potency its a big drop fast. I would have thought my external air line would be as effective as a CO2 scrubber does it just take more time? Will water changes help? I don't do the 20% a month more like 10%.

Thanks again!

That won't really work. The sodium hydroxide is super soluble and will all dissolve in the first batch of water. You can make a solution that has more sodium hydroxide than water in it.

 

[NabberNate]

Well, someone wise mentioned to me... "when was the last time you calibrated your ph probe? " Ummm... a while? After calibration... drum roll. 8.48