Low Alk / High Ca

OceanLab248

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Hey all. Been following the community over the years now and finally decided to create an account and become more active.

I've been in the hobby for ~15 years now. Went from a 25g to my current 40 breeder (bare bottom) ~5 years ago. Unfortunately, I lost interest in the hobby going on a few years now, but I'm trying to get back into things. Over those years, I never took the water parameters, but have always ritually performed a 15g weekly WC (~38%).

So in trying to get back into things again, I just purchased new Hanna checker reagents and my parameters are below over the last 2 days ("Day 1" being the first day after my usual 15g WC):

pH: 7.8-7.9
Nitrate: 0-0.5
Alk: 6.4-6.7
Ca: 499-539
Phos: 0.03
Mag: 1260

My Alk is definitely low and Ca high, so just trying to understand what might be going on and understand best plan of attack (if any at all). I use Reef Crystals, which I know has a higher Alk vs. most salts. I've never dosed or used additives before (never had to). My weekly 15g (~38%) WC has always been sufficient to keep the water parameters stable and where they needed to be back when I used to actually take them (pH: 8.0-8.2, Nitrate: ~0, Alk 8-10, Ca 400-450).

Interestingly, all of my corals look great right now. Nothing is showing any signs of stress or shock. So I'm wondering if my current parameters have actually been my tank's "normal" and everything has been acclimated to that. And which is why I'm not sure if I should leave things as is and just monitor, or try to address - maybe slowly since I don't want to shock anything if the parameters were my tank's "normal" (i.e. maybe a few larger WCs?).

I also tested a fresh batch of mixed salt water to confirm my tests were correct, and those came back typical for Reef Crystals (Alk: 12.6, Ca: 496).

I tried to provide most of the high-level background info, but of course let me know if additional info would be helpful. See below for some additional specs/info and attempted to attach a tank screenshot.

Thanks in advance for the feedback.



Tank: 40 breeder (~5 years old), bare bottom, 2x AI Prime HDs, Vortech MP-10, Aqua Maxx HOB-1.5
Live stock: 2 clowns (received yesterday), 1 coral beauty (received today), prior had a dwarf fuzzy lionfish who just recently died unexpectedly
Coral: LPS dominant, but with some softies and SPS (duncan, plate, trumpet, favia, hammer, frogspawn, torch, lobo, digi, mushrooms, leather, BTA, rock anemone, kenya tree)

PXL_20231202_002506712.jpg
 
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OceanLab248

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Thanks for hopefully looping in others who may be able to assist.

Was also thinking, my Alk 6.4-6.7 measurements 1 and 2 days after already performing a 15g WC is still pretty low. So probably safe to assume the Alk was actually lower leading up to that WC? What could actually cause the Alk to drop so low?

But corals this morning already starting to open up and looking good as the lights are ramping up. In the meantime, thinking about just doing a few WCs today. Thinking maybe 20g (50%)? Or more?
 

Randy Holmes-Farley

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Water changes are a very expensive way to boost alk. I’d just add some baking soda.

This calculator shows how much to use:

 
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OceanLab248

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That calculator tool is amazing - thanks for sending on.

Is there a particular reason my Alk would drop low and Ca high after routine 15g (~38%) WCs? Trying to understand if it might be something I could address proactively vs. needing to continually monitor and add baking soda reactively.

Thanks again for all the feedback on this, all.
 

EricR

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I don't have an answer to your question but your corals look great to me so I'd be wary of trying to bump alk much or at least stretch it out over a long period of time to see how it goes.

It'd be interesting to see alk comparison from right after water change vs a week later before next water change.
 

MarsReefer

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I don’t have a solution for you but I have the same problem with reef crystals salt. I dose alk daily with baking soda. It drops about 1 dkh per week if I don’t dose. I do 10% WC a week. My calcium is at 550 though and I don’t dose it at all.

Dosing baking powder is easy enough though so I haven’t worried about it too much.
 
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Randy Holmes-Farley

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That calculator tool is amazing - thanks for sending on.

Is there a particular reason my Alk would drop low and Ca high after routine 15g (~38%) WCs? Trying to understand if it might be something I could address proactively vs. needing to continually monitor and add baking soda reactively.

Thanks again for all the feedback on this, all.

That’s just the math of consumption. Even if all of the alk depletion is from calcium carbonate deposition and not simply alk depletion from rising nitrate, one will see 2.8 dKH of alk drop (huge and easily detectable) and only 18-20 ppm of calcium de line, which is a much smaller percentage change and is at the edge of reliable detection by kit.
 
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OceanLab248

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Thanks again for all the feedback, everyone. Really do appreciate it.

All corals continued to look amazing throughout the day again, so just decided to continue on with the experiment in measuring the Alk / Ca each day post-WC (~38%). See below for summary across all 3 days now.

Steady 0.3-0.4 decrease in Alk per day, with not too much movement in Ca (+/- 20-30 between days).

Is there a point where I'd definitely want/need to increase Alk if it continues to decrease? This has been my routine for some time now, so I'm not sure I'm anticipating seeing my corals become stressed/shocked.

Day 1:
pH: 7.9
Alk: 6.7
Ca: 539
Nitrate: 0.5
Phos: 0.03
Mg: 1260

Day 2 (only measured Alk, Ca):
Alk: 6.4
Ca: 499

Day 3 (only measured pH, Alk, Ca):
pH: 7.9
Alk: 6.0
Ca: 519
 
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OceanLab248

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Thanks for the feedback.

Knowing my Alk has likely trended low for some time now, what would be the ideal value to shoot for and maintain? Not sure if it's possible to stress/shock the corals by actually raising the Alk to desirable levels, but of course want to stay away from that potential territory since my corals have all been looking great.
 

GARRIGA

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Carbon dosing helps keep my dkh stable by not exporting the nitrates. Now testing macroalgae for the same reasons but mostly to raise my pH by extracting co2. It's working.
 
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OceanLab248

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As always, thanks for the continued feedback, everyone.

Alk was 5.9 earlier today.

I had some pre-mixed salt water ready from when I was thinking about doing a 20g (50%) WC a few days ago, so I went ahead and just did that. I'm thinking going forward, I'll look into the baking soda dosing option, where hopefully it wouldn't be as significant of a dose vs. now.

Anyway, see below for updated water parameters after the 50% WC:

pH: 7.9
Alk: 9.0
Ca: 545
Nitrate: 0.0
Phos: 0.02
Mg: 1410

Looks like the WC was highly successful in bringing the Alk up. Is the high Ca of any concern?

Thanks all.
 
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OceanLab248

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I know it's been 1+ week since last update, but I've been dosing "Randy's Recipe 1 Alkalinity Part" each day, targeting an Alk of 8.0 for now. I've typically been losing 0.6-0.8 per day (testing 7.2-7.4) and bringing back up to ~8.0.

My Ca is also continuing to come down. Was at 545 on 03Dec per above post, and tested at 499 today.

I usually perform a weekly 15g WC. Question is whether I should skip at least this week's WC to continue letting my higher Ca come down? Or would I be fine to continue with the WC?

As always, thanks for all feedback.
 

Uncle99

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I would continue to do the scheduled water changes to keep stable.

You can change the frequency to bi-monthly if you wish, but you’ll need to maintain that new frequency, assuming your nutrients remain in range and stable.

All changes affect chemistry to some degree, I find it best to do the same things in the same volumes, day in day out.
 

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