Chicken/egg problem for Alk/Ca/PH?

[arking_mark]

I transitioned off a 7+ year old tank and I'm 3 months into my new tank and have been struggling with getting my dosing regiment in.

I started with 7ish Alk and a PH between 7.8 and 7.9. I use Brightwell Neomarine salt and have higher CO2 in the house.

I decided to go Kalkwasser to get the PH bump. See this thread:

Advice for a complete supplement dosing that utilizes Kalkwasser

I'm using BSR Kalk and a KS-100 stirrer and pH is reflecting dose added. Last couple of dKH readings have been going up so maybe substrate/rock/CUC was absorbing the initial dosing and now the numbers are rising. With the re-calibrated GHL, my dKH is showing about a .2dKH drop in 6hrs (I...

www.reef2reef.com

I was going ULM, and automated the dosing limiting Alk to no more than 8.5 and PH to 8.3. Interestingly enough, the PH and Alk were both going up as expected and I seemed to be consuming a good amount (.5 to 1dkh a day). Then I had a Kalk reactor leak and had to shut it down for about a day. The PH and Alk prior to that seems stable around 8ish dKH and 8.07. Then the PH dropped as expected but the Alk then continued to rise over 9dkh.

After about a week the Alk came down below 8.5 and the dosing began again...and in 24 my Alk went up by 1dKH...which was about what I was adding in Kalkwasser (as if there was no consumption).

So automation shutoff kalk. Several days later, Alk is below 8.5dKH, and we repeat the cycle:

You can see by the PH readings that the highest peak is where the cutoff happened. But note, the Alk skyrockets after Kalk has been stopped (I don't have a good explanation for this).

Based on many articles, higher PH can have a big effect of Alk/Ca consumption and coral growth. But with my automation (8.5dKH cutoff) my pH would drop...reducing consumption. However, I need consumption to keep dosing Kalk to keep my elevated PH. This becomes a chicken and egg situation.

So to overcome this, I threw in some more faster growing frags (to up consumption) and turned off the automation part and am just dosing .5dKH in 24hrs of Kalkwasser.

I'll monitor the Alk, but focus for now on maintaining a higher PH and see what happens.

My thought is that the higher PH will increase the uptake of Alk/Ca and allow me to continue and eventually increase Kalkwasser dosing.

There are other explanations for my difficulties in getting my parameters locked in. My GHL KH Director may not be accurate...however it mostly syncs up with my Hanna Alk spot checks. It could also be that my initial Kalk dosing wasn't saturated (definitely not based on mS readings...I've switched to a magnetic kalk stirrer that does a much better job at keeping Kalkwasser saturated). My small collection of frags may not be soaking up much Alk/Ca.

Curious on what the R2R Community thinks.

 

[Randy Holmes-Farley]

My thought is that the higher PH will increase the uptake of Alk/Ca and allow me to continue and eventually increase Kalkwasser dosing.

That is certainly the expected result. Higher pH increases the demand for calcium and alkalinity by both corals and abiotic precipitation.

I'm not sure about the rise after stopping dosing unless you are also adding alk some other way (declining nitrate will do it, for example), but the rise is so small that it is also well within alk test specifications.

 

[arking_mark]

That is certainly the expected result. Higher pH increases the demand for calcium and alkalinity by both corals and abiotic precipitation.

I'm not sure about the rise after stopping dosing unless you are also adding alk some other way (declining nitrate will do it, for example), but the rise is so small that it is also well within alk test specifications.

I am certainly hoping that focusing on the pH for now will get me to that happy place.

As to the rise after stopping, it's consistently happened with the automated Alk dosing stop. I can't explain it. It could be within testing accuracy. However, I think something else is going on. It's almost like the dropping pH is effectively causing something to return Alk to the system.

 

[Randy Holmes-Farley]

I certainly hoping that focusing on the pH for now will get me to that happy place.

As to the rise after stopping, it's consistently happened with the automated Alk dosing stop. I can't explain it. It could be within testing accuracy. However, I think something else is going on. It's almost like the dropping pH is effectively causing something to return Alk to the system.

Any chance you are dosing cloudy limewater with particulates in it? those may take time to fully dissolve.

Otherwise, I don't know what it would be, unless it is a process that keeps going forever, in which case it might be the slow dissolution of sand due to the low pH down inside of it.

 

[arking_mark]

Any chance you are dosing cloudy limewater with particulates in it? those may take time to fully dissolve.

Otherwise, I don't know what it would be, unless it is a process that keeps going forever, in which case it might be the slow dissolution of sand due to the low pH down inside of it.

The Kalkwasser is never actually clear for me, but I wouldn't call it cloudy either. It's mixed 4x a day for a minute or two. It usually settles to the picture below in about 30 minutes and never clarifies more. I'm using BRS Kalkwasser.

As for the sand theory, it's certainly possible. I used new sand for the tank.

As for the last 15hrs of nominal kalk dosing, the pH has been steady climbing and seems to be leveling out at 8.15ish (which I'm thrilled at), and the Alk has been consistently at 8.9ish (which I'm ok with). I'm hoping over time I can settle the tank more towards 8ish. We will see.

 

[Randy Holmes-Farley]

OK, so maybe you are delivering some calcium hydroxide particulates that dissolve slowly in the tank. Such particulates are readily 'soluble', but may instantly get a coating of magnesium hydroxide or calcium carbonate around them that slows down the process.

I've not seen anyone track the alk increase after dosing a slurry of calcium hydroxide.

 

[arking_mark]

OK, so maybe you are delivering some calcium hydroxide particulates that dissolve slowly in the tank. Such particulates are readily 'soluble', but may instantly get a coating of magnesium hydroxide or calcium carbonate around them that slows down the process.

I've not seen anyone track the alk increase after dosing a slurry of calcium hydroxide.

Interesting. Should the Kalkwasser clarify more?

I haven't used this stuff for like 20 years when I was dosing it for my 1st reef tank. It's the pharma grade stuff...I just figured it doesn't clarify more.

When it mixes, it become opaque milk.

 

[Randy Holmes-Farley]

Interesting. Should the Kalkwasser clarify more?

I haven't used this stuff for like 20 years when I was dosing it for my 1st reef tank. It's the pharma grade stuff...I just figured it doesn't clarify more.

When it mixes, it become opaque milk.

It can settle clear, but sometimes, if the particle size is small or air is getting to it, it may not. Settling takes a fair time. Like overnight in a Brute can.

 

[arking_mark]

It can settle clear, but sometimes, if the particle size is small or air is getting to it, it may not. Settling takes a fair time. Like overnight in a Brute can.

The BRS stuff is like dust. What you saw was 6 hours of settling. I could mix once a day or even less frequent.

 

[arking_mark]

Too short a time period to tell, but 24 hrs in, my pH has hit an all time high of 8.22 and the Alk seems to be trending down to about 8.6ish. We will see where this goes, but focusing on the pH seems to be unlocking my target sweet spot! I have high hopes.

Another big thank you to @Randy Holmes-Farley !!!!

 

[ReefBeta]

It's amazing that you get that much pH rise with just kalk. I'm already adding kalk to the evaporation limit, and it can't even counter the fall from lights off. I think it contributed for less than 0.1 pH rise. I have to use a CO2 scrubber to get some meaningful pH impact.

Increase kalk dose results in lower alk because of high pH is interesting. Looking forward to see how it pans out long term.

I also see a couple times that the alkalinity jump or fall for more than 0.5 dkh in 6 hours for no apparent reason. Dosing was not changed and variation before and after are less than 0.2 daily. Not sure if related or not. But the particulates could be an explanation from what I saw.

 

[arking_mark]

It's amazing that you get that much pH rise with just kalk. I'm already adding kalk to the evaporation limit, and it can't even counter the fall from lights off. I think it contributed for less than 0.1 pH rise. I have to use a CO2 scrubber to get some meaningful pH impact.

Increase kalk dose results in lower alk because of high pH is interesting. Looking forward to see how it pans out long term.

I also see a couple times that the alkalinity jump or fall for more than 0.5 dkh in 6 hours for no apparent reason. Dosing was not changed and variation before and after are less than 0.2 daily. Not sure if related or not. But the particulates could be an explanation from what I saw.

You are correct. The Alk swings have been a little brutal and not always correlated with dosing. I'm using the BRS pharma kalk and the reactor per instructions. I could reduce mixing to once a day...but I'm liking the results so far and the Alk level is actually trending down. Again the dosing rate is 1.5ml/min which is about a drop every 5 seconds. Additionally, it enters a very high flow area of the sump. ILL keep monitoring and provide updates.

Another reefer has indicated that they also found a better boost with slow dripping. Today's pH boost was probably helped by a lot of doors being opened and closed throughout the day.

 

[arking_mark]

Thinking on the pH. My typical range was 7.8 to 7.9. I'm now seeming staying above 8.15...I don't believe this is due just to Kalkwasser. There are two other factors:
1. I added a skimmer for better gas exchange about a week ago
2. My back patio doors are broken and basically leaking outside air like cracking open a window.

I'm guessing 1 and 2 combined to give me a good boost of about .15 bump. When kalk dosing was paused I dropped down to about 8.03. I feel the Kalkwasser is probably giving me a .12ish bump.

I'm dosing 1800 ml a day which is about .4% of tank volume. So I think that's about right.

 

[arking_mark]

A picture to illustrate my experience so far...

The RED arrow indicates where my automation shut off the kalk dosing (Alk was above my 8.5 high limits).

The BLUE arrow indicates where I decided to change my dosing regiment to a constant nominal dose of 1.5ml/min which is about 1800ml for my 400L tank (a .5dKH replacement)

As you can see, the Alk continued to rise after the stop. It looks like it lags the dosing...which may be due to my less than clear Kalkwasser.

With the nominal dosing, it appears my Alk may be settling in between 8.6dKH and 9dKH.

Again, too short a time period to assess anything...but it trending in the direction I was looking for.

 

[arking_mark]

@Randy Holmes-Farley So I have another unexpected jump in dKH. My readings have been between 8.6 and 8.9. At 6pm yesterday they jumped to 9.5 and have been slowly coming back down. 6am was 9.2dKH and 9am was 9.1. pH has stayed over 8.15...and I did not alter kalk dosing.

I'm wondering if this has something to do with my Brightwell Neomarine salt and 1% AWC.

If you recall, several month ago when I was switching salts on my old tank from IO RC to Neomarine, I had unexpected Alk readings. The ASW was 7ish and months after the switch, my Alk readings would be much higher than expected preventing me from dosing Triton. Anytime it would drop below 8 any dosing would elevate it for weeks. The only thing in common with these tanks is the salt.

Thoughts on if/how the Neomarine salt might be impacting my Alk?

 

[arking_mark]

OK, so maybe you are delivering some calcium hydroxide particulates that dissolve slowly in the tank. Such particulates are readily 'soluble', but may instantly get a coating of magnesium hydroxide or calcium carbonate around them that slows down the process.

I've not seen anyone track the alk increase after dosing a slurry of calcium hydroxide.

I also let the Kalk sit unmixed for 18hrs. It did not clarify further.

 

[Randy Holmes-Farley]

I also let the Kalk sit unmixed for 18hrs. It did not clarify further.

Mine always did, but finer particle size may not.

 

[arking_mark]

For those following along, the dKH has now settled at 9dKH-ish. The pH boost still has me averaging around 8.15.

I'm changing salts from Brightwell Neomarine to Tropic Marin Pro. I'm not sure this will have any impact, but this is now 2 tanks that aren't reacting in expected manners to dosing and Alk. The only thing in common is the salt.

It will be a slow 1% daily AWC, so I don't expect any impacts. The salts are actually very similar in Alk/Ca levels.

 

[arking_mark]

For those following along, my Alk continues to creep up and I'm now averaging 9.4ish.

I have reduced kalk dosing to .75ml/min which should equate to .25dKH. We will see how this impacts pH.

I have ordered a media reactor and CO2 scubbing media and will try to leverage that to maintain my pH.

My bet is that the tank is consuming very little Alk at this stage. Or if I believe my Alk reading, it's consumed more haphazardly.

 

[arking_mark]

So I installed the CO2 scrubber this afternoon and hit a new pH high of 8.24.

I've heard the CO2 scrubbers can be too effective...so I'm monitoring closely and will take it offline if it continues to climb.

Anyway, my pH average is still 8.15 as I've been between 8.06 and 8.22 over the last several days...