Alk supplement raising CA

flat6guy · Mar 2, 2021

Like the title says, my Alk supplement is raising the Ca level significantly. I recently setup an Apex trident for it's ability to test the parameters for me. I watched the tank for 14 days before intervening as the tank has been setup for 2 years. I performed my weekly water changes in the monitoring phase. I noticed the Alk was dropping at what I'd consider a decent amount in between water changes. It was starting at 8,5ish and dropped to 7.6 in a few days. After seeing the trend I can now make the correlation to my corals being happiest after a water change and getting irritated by the time it was time for another. I purchased a small bottle of alk supplement from the local fish store. The brand is Fluval Sea. It does seem to have some effect on the alk levels but honestly I'm seeing a much larger spike in Ca levels then the alk levels.

My tank is a Fluval M60 34g tank. I initially read the directions on the bottle. It states to add 10ml per 50 gals each week. I opted to add 10ml to start with. Shoulda done a smaller amount as my alk went from 7.6 to 8.5. Whoops! I then start dosing smaller amounts as the alk started to drop down again. I added .25ml when the alk dropped to 8.2. The alk level dropped to 8.1 by the next morning. Added .5ml. Didn't go up and still went down so the next day I added 1.0ml. This caused the alk to rise to 8.47. I'm aiming for 8.5 as I have a mixed reef tank with some Monti. SPS corals. Trying to keep things stable.

So what I noticed tonight was the Ca has risen to 520. I'm curious if anyone else uses this supplement and has had similar results. I've read the bottle twice now. I don't see any mention of this having a Ca supplement or being a two part dose in one bottle.

arking_mark · Mar 2, 2021

Usually Alk and Calcium are consumed together. That's why many people get their tank balanced and then dose a supplement that maintains the balance (i.e. 2-part, Kalk, All-for-reef).

If you're just adding Alk and your Ca is swinging, I'd suspect the test.

flat6guy · Mar 2, 2021

I feel like an idiot. My trident had an error message that I resolved tonight. After the resolution I found the CA at 520. The previous test had it at 480 so I didn't think much of it. While posting this I ran the tests again. This time the CA is 446 which is right around the normal average it's been at for the past 2 weeks.

As for the alk supplement only. That's because I'm only seeing a drop in the alk. The calcium hasn't dropped below 415. The ca and mg are tested twice a day and remain relatively steady with a minor drop over the week between water changes. I'm only intervening on the alk in an effort to keep it around 8.5 so that I can in hopes raise my ph that is low. My ph hovers around 7.6-7.7.

I've tried increasing surface agitation. Venting the skimmer intake outside. Opening windows this time of the year isn't an option as it's pretty cold. Windchill's today were way below zero. I've recently added a Santa Monica filter to help reduce nutrient levels some. This is supposed to help take up some CO2 in the tank which should help my ph. I've also purchased a CO2 scrubber that should be here later this week. I'd love to see my ph above 8.0

Wondering if I can get ph above 8 if the calcium uptake will increase

arking_mark · Mar 2, 2021

flat6guy said:
I feel like an idiot. My trident had an error message that I resolved tonight. After the resolution I found the CA at 520. The previous test had it at 480 so I didn't think much of it. While posting this I ran the tests again. This time the CA is 446 which is right around the normal average it's been at for the past 2 weeks.

As for the alk supplement only. That's because I'm only seeing a drop in the alk. The calcium hasn't dropped below 415. The ca and mg are tested twice a day and remain relatively steady with a minor drop over the week between water changes. I'm only intervening on the alk in an effort to keep it around 8.5 so that I can in hopes raise my ph that is low. My ph hovers around 7.6-7.7.

I've tried increasing surface agitation. Venting the skimmer intake outside. Opening windows this time of the year isn't an option as it's pretty cold. Windchill's today were way below zero. I've recently added a Santa Monica filter to help reduce nutrient levels some. This is supposed to help take up some CO2 in the tank which should help my ph. I've also purchased a CO2 scrubber that should be here later this week. I'd love to see my ph above 8.0

Wondering if I can get ph above 8 if the calcium uptake will increase

I've had an interesting journey to go ultra-low maintenance. I'll skip most of the journey, but I was also getting a low pH due to high home CO2. This led to Kalk dosing for added pH boost, then to a skimmer for better aeration, and then to CO2 scrubber.

Kalk + Skimmer + CO2 Scrubber = Awesome pH! I went from a daily swing of 7.8 to 7.9 to 8.26 to 8.36!

flat6guy · Mar 2, 2021

I've recently bought a CO2 meter from amazon. Should be here next week. Very curious to see how much C02 is in the house with the wife, kid and two dogs.
I've upgraded my skimmer to a Tunze skimmer awhile ago. Major improvement over the fluval skimmer that came with the tank. I tossed that thing. All but worthless.
At this point the apex is helping me work towards a low maintenance tank. It'll be awhile before I'm there. The next step will be an auto water changer. My busy season is around the corner and this teds to be when the tank suffers.

arking_mark · Mar 2, 2021

flat6guy said:
I've recently bought a CO2 meter from amazon. Should be here next week. Very curious to see how much C02 is in the house with the wife, kid and two dogs.
I've upgraded my skimmer to a Tunze skimmer awhile ago. Major improvement over the fluval skimmer that came with the tank. I tossed that thing. All but worthless.
At this point the apex is helping me work towards a low maintenance tank. It'll be awhile before I'm there. The next step will be an auto water changer. My busy season is around the corner and this teds to be when the tank suffers.

Been there done that. I'm almost completely automated at this point...Just finalizing my dosing regiment and dialing in numbers...hence the changes made for pH.

arking_mark · Mar 2, 2021

arking_mark said:
I've had an interesting journey to go ultra-low maintenance. I'll skip most of the journey, but I was also getting a low pH due to high home CO2. This led to Kalk dosing for added pH boost, then to a skimmer for better aeration, and then to CO2 scrubber.

Kalk + Skimmer + CO2 Scrubber = Awesome pH! I went from a daily swing of 7.8 to 7.9 to 8.26 to 8.36!

The red arrow is when CO2 scrubber came online.

Randy Holmes-Farley · Mar 3, 2021

flat6guy said:
Wondering if I can get ph above 8 if the calcium uptake will increase

I don't believe there is a lack of calcium consumption.

Assuming nitrate is not rising, calcium likely is being depleted at a rate appropriate for the alk drop, but on a percentage basis, it is always much lower (because seawater has a far bigger reservoir of calcium than alkalinity) and typically hard to readily detect by testing without waiting longer since test methods are not good at detecting small changes in calcium.

Couple that with salt mixes that can contain high amounts of calcium, and folks often think calcium is stable when it is actually being depleted at the expected rate.

flat6guy · Mar 14, 2021

Randy or someone that knows. Can alkalinity levels drop from rising Nitrate levels? I ask as I'm seeing a 0.8 drop in alk over a 48 hour period. There is a nuisance algae problem that I'm working at. I've purchased a dosing pump and BRS 2 part supplements. Awaiting there arrival. In the meantime I want to understand if my tank is dropping due to coral, inverts, and coralline or from some other source I'm not aware of

Randy Holmes-Farley · Mar 15, 2021

flat6guy said:
Randy or someone that knows. Can alkalinity levels drop from rising Nitrate levels? I ask as I'm seeing a 0.8 drop in alk over a 48 hour period. There is a nuisance algae problem that I'm working at. I've purchased a dosing pump and BRS 2 part supplements. Awaiting there arrival. In the meantime I want to understand if my tank is dropping due to coral, inverts, and coralline or from some other source I'm not aware of

Yes, but I doubt it is accounting for that fast of a drop.

A rise of 50 ppm depletes 4.5 dKH of alkalinity:

When Do Calcium and Alkalinity Demand Not Exactly Balance? by Randy Holmes-Farley - Reefkeeping.com

Alkalinity Decline in the Nitrogen Cycle

One of the best known chemical cycles in aquaria is the nitrogen cycle. In it, ammonia excreted by fish and other organisms is converted into nitrate. This conversion produces acid, H+ (or uses alkalinity depending on how one chooses to look at it), as shown in equation 1:

(1) NH3 + 2O2 --> NO3- + H+ + H2O
For each ammonia molecule converted into nitrate, one hydrogen ion (H+) is produced. If nitrate is allowed to accumulate to 50 ppm, the addition of this acid will deplete 0.8 meq/L (2.3 dKH) of alkalinity.

However, the news is not all bad. When this nitrate proceeds further along the nitrogen cycle, depleted alkalinity is returned in exactly the amount lost. For example, if the nitrate is allowed to be converted into N2 in a sand bed, one of the products is bicarbonate, as shown in equation 2 (below) for the breakdown of glucose and nitrate under typical anoxic conditions as might happen in a deep sand bed:

(2) 4NO3- + 5/6 C6H12O6 (glucose) + 4H2O --> 2 N2 + 7H2O + 4HCO3- + CO2

In equation 2 we see that exactly one bicarbonate ion is produced for each nitrate ion consumed. Consequently, the alkalinity gain is 0.8 meq/L (2.3 dKH) for every 50 ppm of nitrate consumed.

Likewise, equation 3 (below) shows the uptake of nitrate and CO2 into macroalgae to form typical organic molecules:

(3) 122 CO2 + 122 H2O + 16 NO3- --> C106H260O106N16 + 138 O2 + 16 HCO3-

Again, one bicarbonate ion is produced for each nitrate ion consumed.

It turns out that as long as the nitrate concentration is stable, regardless of its actual value, there is no ongoing net depletion of alkalinity. Of course, alkalinity was depleted to reach that value, but once it stabilizes, there is no continuing alkalinity depletion because the export processes described above are exactly balancing the depletion from nitrification (the conversion of ammonia to nitrate).

There are, however, circumstances where the alkalinity is lost in the conversion of ammonia to nitrate, and is never returned. The most likely scenario to be important in reef aquaria is when nitrate is removed through water changes. In that case, each water change takes out some nitrate, and if the system produces nitrate to get back to some stable level, the alkalinity again becomes depleted.

If, for example, nitrate averages 50 ppm at each water change, then over the course of a year with 10 water changes of 20% each, the alkalinity will be depleted by 1.6 meq/L (4.5 dKH) over the course of that entire time period. This process is one of the primary reasons that fish-only aquaria that often export nitrate in water changes need occasional buffer additions to replace that depleted alkalinity.