Almost got it! Kalk spikes alk on refill

[Saltyanimals]

My journey back to kalk from a CaRX has been a rocky one trying to solve for pH, but I'm close. I finally figured out that I need the kalk stirrer to run 24/7 in order to keep the solution saturated enough to actually dose potent kalk. Running it periodically through various stir schedules doesn't work for me. I even increased the stirrer speed (DC motor) to keep more suspended and milkier kalk water finally solved my kalk potency issues.

The issues:

pH is now stable and within my desired ranges. Alk on the other hand is a roller coaster. I'm diligent with checking at the same time everyday and keeping a pH and Alk log. I see the following patterns after a fresh kalk reload:
- pH and Alk immediately spikes (Problem #1)
- pH and Alk stabilizes in about 24-48 back to normal ranges and stays here for 3-4 days (Problem #2)
- Alk starts to drop and requires kalk reload and repeats this cycle. I see the solution becoming more clear assuming less kalk in saturation. I don't think I have a dissolution issue because I don't visually see alot of kalk residual at the bottom if I turn off the stirrer and allow it to settle.


Problem 1:
- Alk spike is significant. Based on my consumption, 5 tbsp of kalk in my stirrer spikes alk ~ 1 dkh immediately and stays there for at least 24 hrs. This will last only 3-4 days. A higher refill amount will get more time, but will spike alk 2+ dKh which is causing issues. Because of this spike, I almost have to time the refill in a way that requires me to let alk drift down to a level that would accommodate the spike. i.e. allow alk to drop 2.0 dkh to anticipate the 2.0 alk spike on the refill. No joy in the alk rollercoaster.

Problem 2:
- a higher 10 tbsp refill will get me more time, but now we're talking 6-8 days total at the risk of the 2 dKH alk spike. No where near any of the experiences I've read where folks refill 2-4 weeks at a time.

I can't see how this can be normal and not cause issues on SPS tanks. Is everyone else timing their refills to accommodate the spikes and just refilling every few days? Much higher maintenance than I thought.

 

[therootcause]

Hello. Can you provide some simple details to help me understand?

How large is your stirrer and how many mL's are you dosing per day and at what frequency? Does your ATO add freshwater in to the stirrer and the stirrer spills into the tank or are you dosing RO into the stirrer at a set rate and subsequently that rate is delivered to the aquarium as concentrated kalkwasser?

If Kalkwasser is at full concentration with 5 tbsp then it should remain the same concentration when you add 10tbsp of powder and the alk swing that you experience would be the same. Something is not right.

*I do not use a stirrer, but I mix Kalkwasser at full concentration into a 5 gallon pail that I dose to the tank over approximately 12 days.*

Edit: If you have your Alk and pH logs available to share I am curious to overlay your dosing schedule to the logs.

 

[Randy Holmes-Farley]

If you are literally dosing milky limewater (kalkwasser) then yes, it will be extra strong when first refilled since there are more solids to suspend and will lead to this roller coaster.

 

[Someshmuk]

If you are literally dosing milky limewater (kalkwasser) then yes, it will be extra strong when first refilled since there are more solids to suspend and will lead to this roller coaster.

To add, if you're dosing milky kalkwasser it would be hard to determine the amount of actual kalk being dispensed into the tank since it's past the measured clear and saturated calculation and judging the density of "milkyness" by eye is not studied and changes as the kalk settles out.

 

[Saltyanimals]

Thanks all!. Stirrer container is 5Liter. Fresh ATO water 3860ml daily (160ml every hour x 24 hours) into a 180G system.

I had issues with kalk potency initially. Fresh newly bought kalk. Stirrer running for 5 mins every few hours could not maintain alk. Playing with the schedule and looking at my graphs, I noticed the stability increased as I went to hourly and even more so when I had it stir a few minutes before the hourly dose. Eventually got to a point where I just left it stirring 24/7 which where I'm now getting the milky kalk which stays stable for few days.


Graph: the 8.02 pH highlighted is the refill point. Notice the pH pike later that day. Settles down over next 2 days and continues to drift down. The farthest left of this graph (first measure) is also another refill point. Again showing the pattern on the pH. This is so predictable, that I ignore the pH graph the next 48 hrs.

Alk: 8.79 dKH at refill to an immediate 9.8 dKH and stays there 24 hours later with the 5 tbsp. This is very predictable ~1 dkh spike. 10 tbsl gives me a 2.17 dkH spike also very predictable.


edited:

I just took a quick alk test a bit earlier than usual to keep this discussion fresh. Sure enough, alk is 9.3 which is a 0.6dkh drop from this time yesterday which historically tells me I need to refill my kalk. I can bet that a refill now will land me +1 dkh or 10.3 this time tomorrow.

At this pace my alk rollercoaster will continue to climb over time unless I allow it to drop first.

Also note that my stirrer is on DC motor, so I can control the speed. I keep it fairly low, but enough to see kalk particulates suspended as expected with a constant stir.

 

[therootcause]

It sounds like what @Randy Holmes-Farley said, which is that you are dosing more solids when you refill the container and by day two many of the solids have either been dissolved or there are less floating in the water column to be dosed into the tank.

I also agree with @Someshmuk that you really don't know what you are dosing when milky solids are being sent directly to the tank.

I forget if there was a question or not at the beginning. It sounds like you solved the initial problem which was that you were unable to keep up with demand. It sounds to me like you are throwing a hand grenade at the tank each week to solve a problem that may need something more precise in the long term.

 

[Randy Holmes-Farley]

Yes, the update is consistent with the initial analysis. I’m not a big fan of kalk stirrers, and am even less a fan of trying to dose a kalk slurry as you are doing, in part for the reasons you are finding, and part out of concern for the particles landing on delicate organisms before fully dissolving.

 

[Saltyanimals]

You guys are spot on with my observations. I had to increase the stirrer speed/frequency to keep the potency high enough otherwise it won't maintain alk. Shining a light I clearly see the solids which is being dosed as it is constantly stirred into suspension.

I just refilled 7 tbls kalk. Allowed it to settle first for a few minutes before turning on the stirrer so I have about 45 mins before the next hourly dose. Looking at the history, I'll expect higher than a 1dkh (7 tbsp vs 5 tbsp previously) at this point tomorrow. I'll also expect pH spike over the next few hours following the pattern in the graph above.

The weekly grenade analogy is accurate, but does that mean my experience is the norm for kalk stirrer users? And I can't see how this would not cause issues. Enough people are doing kalk again and I haven't read similar concerns. Going back to turning off the stirrer and allowing it to settle (taking the stirrer part out) would reduce the solids, but again it's not keeping up even though I'm at the kalk calculators estimates.

How is everyone else doing it? Thanks!

 

[Someshmuk]

You guys are spot on with my observations. I had to increase the stirrer speed/frequency to keep the potency high enough otherwise it won't maintain alk. Shining a light I clearly see the solids which is being dosed as it is constantly stirred into suspension.

I just refilled 7 tbls kalk. Allowed it to settle first for a few minutes before turning on the stirrer so I have about 45 mins before the next hourly dose. Looking at the history, I'll expect higher than a 1dkh (7 tbsp vs 5 tbsp previously) at this point tomorrow. I'll also expect pH spike over the next few hours following the pattern in the graph above.

The weekly grenade analogy is accurate, but does that mean my experience is the norm for kalk stirrer users? And I can't see how this would not cause issues. Enough people are doing kalk again and I haven't read similar concerns. Going back to turning off the stirrer and allowing it to settle (taking the stirrer part out) would reduce the solids, but again it's not keeping up even though I'm at the kalk calculators estimates.

How is everyone else doing it? Thanks!

I run both Kalk and a calcium reactor with no supplemental dosing now and they even the ph gains/losses.

Before, when i was doing only dosing, I'd set the kalkwasser to dose out clear kalkwasser at a high volume but well below the evaporation rate of the tank. Then supplement any needed corrections with sodium hydroxide/carbonate/bicarbonate and calcium chloride.

You're facing an issue where your tank's alkalinity consumption is greater than the maximum kalkwasser dosage you can supply in a day.

If you have access to a programmable doser, then this is probably the route you'll need to take if you're not wanting to set up a calcium reactor.

 

[Saltyanimals]

I run both Kalk and a calcium reactor with no supplemental dosing now and they even the ph gains/losses.

Before, when i was doing only dosing, I'd set the kalkwasser to dose out clear kalkwasser at a high volume but well below the evaporation rate of the tank. Then supplement any needed corrections with sodium hydroxide/carbonate/bicarbonate and calcium chloride.

You're facing an issue where your tank's alkalinity consumption is greater than the maximum kalkwasser dosage you can supply in a day.

If you have access to a programmable doser, then this is probably the route you'll need to take if you're not wanting to set up a calcium reactor.

Hi @Someshmuk you highlighted an interesting point. I also run a CaRX, but it's turned down at the moment while I'm experimenting with Kalk again. It's not OFF, but very low effluent volume. The CaRX wasn't working for me because of the pH impact combined with a biopellet reactor (major pH depressor) together is a significant impact to pH. Hitting 7.9 pH was a dream. Without going much on a tangent there, I needed something else. And here we are.

During this experiment run, the mindset was to have kalk reactor be the primary and CaRX as the secondary/supplemental source of alk. Following your comment, it appears I may have hit the kalk wall and I keep trying to push it higher with basically slurry. It feels like I may just need to turn kalk down and simply increase the CaRX again to a balance. This should extend my kalk refill time by allowing me to run the kalk at a lower volume.

How would you describe your system in terms of CaRX or Kalk as the primary or supplemental systems? 50/50? 30/70?

 

[Saltyanimals]

2 week update from above:

Having gone through now 2 kalk refill events, my personal tank experience from my log tells me:


- Expect the kalk powder refill to spike your alk. Amount of the spike however can be mitigated. i.e. 2 weeks ago I reduced my kalk vol 20% and turning the CaRX back up to pick up some of the slack. This 20% reduction helped reduce the Alk spike. I went from a predictable 1 dkh spike every time now to a 50-60% which is tolerable. This makes sense.
- Earlier I commented on up to 2 dkh spike based on the amount of kalk I refilled speculating more kalk powder = higher spike. That was wrong. It wasn't the amount, but the stirrer speed which put more into suspension proportional to the dosing vol.
-I increased my kalk powder this time to almost 3/4 cup without seeing that 2dkh spike. Gives me some comfort that I'll move to 1 cup during the next refill and gradually move up from there and will watch how much time I get between refills. Getting to 14 days is sufficient for me


Biggest take away is that the kalk reactor alone wouldn't give me the stability which takes this back to the original question. How do high demand SPS tanks make it with a kalk stirrer alone? Doesn't seem possible from my humble experience without something else supplementing like a CaRX or 2/3 part. My pH problem appears to be solved for now.

 

[Randy Holmes-Farley]

Biggest take away is that the kalk reactor alone wouldn't give me the stability which takes this back to the original question. How do high demand SPS tanks make it with a kalk stirrer alone? Doesn't seem possible from my humble experience without something else supplementing like a CaRX or 2/3 part.

You are right, they typically don’t. You cannot get more than about 2 dKH per day from kalkwasser with typical evaporation rates.

FWIW, I’m not a fan of stirrers anyway and prefer dosing from a reservoir, but the evaporation limitation remains.

 

[Dmax]

I have also questioned this. Seen numerous tank videos on youtube with wall to wall sps claiming only supplementation is a Kalk reactor.

This is my first time trying to only run off Kalk. All other tanks I ran a CARX and Kalk. Light on the kalk demand and really only used at night for a ph boost.

I experience the same problem just not as large. When I top off the Kalk in my reactor every Sunday my Alk will rise for 12-24 hours and takes the PH a couple days to settle back to normal. I'm dosing 83ml a hour and I believe is why I'm not seeing such large swings.

I wonder if your seeing the large swing from the kalk not having time to settle in the reactor before pushing 160ml thru it? Dosing more of the slurry in the first 2 hours or so?

 

[Saltyanimals]

The large swing IS from the unsettled Kalk since I’m using a stirrer. I played with various stirrer speeds and concluded (for my tank) that I have to suspend and dose some of that slurry otherwise I don’t have fully saturated / lower potency Kalk water. This part is still a mystery since Kalk has a known saturation and no reason to believe a good stir wouldn’t keep it saturated to dose shortly after allowing it to settle. I see quick downward drifts when I dosed the clear water per my logs and testing. I’ve turned down the Kalk a bit closer to 100 ml/hr and turned up turn carx to pick up the slack. This should give me less swing to your point but supports the Kalk only challenges for SPS tanks. No joy.

Randy will remind us that he doesn’t love the stirrer either but I don’t have the space for 30-50 gallon Kalk storage. Looks like Kalk plus carx for me until the next trend arrives. lol