My corals are consuming dKH at an absurd rate

[oldkiddo1990]

Hi everyone, I’m dealing with a problem that I just can’t figure out. These are my current tank parameters:

* Total system volume: 450 liters including the sump
* Alk: 7 dKH
* Ca: 490
* Mg: 1350
* PO4: 0.03
* NO3: 5 ppm

As you can see in the photos, this is the entire coral stock currently in my tank - mostly small SPS frags with a few soft corals. But the tank is consuming dKH at an absolutely crazy rate.

I’m using the alkalinity supplement from Coral Essentials, the powdered version mixed with RODI water at a concentration of 180,000 ppm (following the mixing instructions on Coral Essentials’ website). According to their calculator, just 45 ml of this solution should raise alkalinity by 1 dKH in my system.

But right now I’m dosing 120 ml per day (split into 10 doses), and the tank still stays around 7 dKH constantly, I can’t get it to increase at all.

For the amount of coral I currently have, does this level of alkalinity consumption seem unreasonable to you guys?

 

[Peer.Boerner]

I hate to ask, but (1) what is your salinity and more importantly, (2) are you absolutely positive your Alk test s accurate? I hope you get to the bottom of this!

 

[oldkiddo1990]

I hate to ask, but (1) what is your salinity and more importantly, (2) are you absolutely positive your Alk test s accurate? I hope you get to the bottom of this!

Thanks for asking
honestly, those basic details definitely needed to be clarified first.

The tank’s salinity is consistently at 1.025. And I’m also very confident in the test results because I use both Salifert and Hanna test kits, and I test at the same time every day. The Salifert test consistently reads between 7.1 and 7.3 dKH, while the Hanna Instruments checker always shows somewhere between 6.9 and 7.2 dKH.

 

[Peer.Boerner]

Thanks for asking
honestly, those basic details definitely needed to be clarified first.

The tank’s salinity is consistently at 1.025. And I’m also very confident in the test results because I use both Salifert and Hanna test kits, and I test at the same time every day. The Salifert test consistently reads between 7.1 and 7.3 dKH, while the Hanna Instruments checker always shows somewhere between 6.9 and 7.2 dKH.

That all sounds good to me. I use the same gear. I’m going to follow and learn from your experience.

 

[Randy Holmes-Farley Verified Community Expert]

I did not check the math, but if that sand is new dry sand, it will be acting as a seed for precipitation of calcium carbonate until it gets coated with organic, phosphate, bacteria, etc.

In the mean time, I'd use just baking soda, not sodium carbonate, because higher pH facilitates such precipitation.

 

[dangles]

Are you sure it’s not precipitating? Your calcium/mag look ok so maybe not but worth considering.

*edit - just saw Randy’s post

 

[oldkiddo1990]

Are you sure it’s not precipitating? Your calcium/mag look ok so maybe not but worth considering.

*edit - just saw Randy’s post

I’ve heard about that too, and it could definitely be one of the causes.
But honestly, I have no idea what signs I should even look for to tell whether precipitation is actually happening. I’m not seeing any obvious symptoms like cloudy water, and both my Ca and Mg levels are completely normal.

The dosing tube outlets in the sump’s return pump chamber are placed far apart from each other, and each solution is dosed 1–2 hours apart as well. So it seems pretty unlikely that precipitation is occurring. And even if it really is happening, I honestly don’t know what else I could do besides spacing the dosing tube outlets even farther apart in the return chamber

 

[Randy Holmes-Farley Verified Community Expert]

Sand hardening and pumps seizing up are the main signs.

Also, maybe the math is off or the product is not as potent as it claims.

If you do not see these issues, I'd just keep dosing.

 

[oldkiddo1990]

I did not check the math, but if that sand is new dry sand, it will be acting as a seed for precipitation of calcium carbonate until it gets coated with organic, phosphate, bacteria, etc.

In the mean time, I'd use just baking soda, not sodium carbonate, because higher pH facilitates such precipitation.

My tank doesn’t have any sand, and the rockwork is already completely covered in algae/biofilm. The tank itself is also close to a year old by now.

As for pH, it ranges between 8.15 and 8.33, which is actually pretty great.

Seriously, I have no idea what the heck is consuming all my dKH.

 

[Randy Holmes-Farley Verified Community Expert]

Oh, that's a bare bottom? I was fooled by the picture. What are the rocks?

If you do not see excessive precipitation on heaters and pumps (anything warm), then there is no precipitation issue.

 

[oldkiddo1990]

Oh, that's a bare bottom? I was fooled by the picture. What are the rocks?

If you do not see excessive precipitation on heaters and pumps (anything warm), then there is no precipitation issue.

I honestly don’t see any abnormal signs other than the insanely high dKH consumption.
Hmm… and the scariest part is ruling out every possible cause and still not being able to find the exact reason behind it

Maybe I should try switching to a different brand of supplements/chemicals and see what happens.

 

[Randy Holmes-Farley Verified Community Expert]

I honestly don’t see any abnormal signs other than the insanely high dKH consumption.
Hmm… and the scariest part is ruling out every possible cause and still not being able to find the exact reason behind it

Maybe I should try switching to a different brand of supplements/chemicals and see what happens.

I'd try just baking soda for a while and see if there's a potency or math issue. They may have a mistake in their assertions.

 

[oldkiddo1990]

I honestly don’t see any abnormal signs other than the insanely high dKH consumption.
Hmm… and the scariest part is ruling out every possible cause and still not being able to find the exact reason behind it

Maybe I should try switching to a different brand of supplements/chemicals and see what happens.

I'd try just baking soda for a while and see if there's a potency or math issue. They may have a mistake in their assertions.

Could you be abit more specific? Whats the recipe for mixing baking soda, what ratio should I use? And how many ml of the solution made from that recipe should I start dosing per 100 liters of tank water?

 

[Peer.Boerner]

Could you be abit more specific? Whats the recipe for mixing baking soda, what ratio should I use? And how many ml of the solution made from that recipe should I start dosing per 100 liters of tank water?

You can go to the main page of this forum and there is a list of calculator links. I use this one and get good results. https://reefapp.net/en/dosing-calculator

 

[Randy Holmes-Farley Verified Community Expert]

This calculator shows how much baking soda it takes to boost alk:


https://reef.diesyst.com/chemcalc/chem_calc3.html

 

[schooncw]

my 120 is loaded w coral and I add SeaChem Reefbuilder to maintain alk, as it is consumed very quickly. I used Salifert but got Hanna for alk and really like the kit. I also use Reef crystals, which runs around 12dkh.