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Cultivated Reef

IM 10gal Reef Water Chemistry


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Hey all!

You can follow my tank build HERE


Hitting the 2 month mark, the frags seem to be pulling out a HUGE amount of dKH & Ca. I do not know if this volume is normal as this is my first dosing experience.


So here are the parameters so far. 


June 02 = results after the WC


P = 0.138ppm

dKH = 7.5.dKH

Ca = 475ppm

NO3 = 5ppm


June 10 = results before the WC


P = 6ppb

dKH = 5.9dKH

Ca = 200ppm


June 10 = results after the WC


P= 1ppb

dKH = 7.3dKH

Ca = 250ppm


Did a second WC on June 10 after a few hours = 


dKH = 8.9dKH


June 12 = results after the WC


P = 2ppb

dKH = 8.1dKH

Ca = 220ppm


I haven't tested for magnesium because it hasn't arrived.


I am also convinced my calcium testing is wrong. I tested a new batch of saltwater and the result was 200ppm. Could it have precipitated? I am using FRITZ Salt mix. I will make a fresh batch of saltwater and test it within 20 minutes of mixing and get back to you guys on this.


In the meantime, are these numbers normal?


How should I dose? I am willing to try manual dosing until I get the hang of it, then I will get a doser, timer, etc.


I would really appreciate the help here since I am new to dosing, this is my first reeftank with hard corals, and it seems to be going very well, I just need help graduating.


As far as I understand my tank is consuming roughly 1dKH per 24 hrs. What is the best way to dose this? I am thinking about buying THISWhat do you guys think?


Thanks for reading!




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I would assume you are dosing 2 part or All For Reef?

I had a similar experience with my current tank in the earlier months.

So I double checked my testing then started dosing All For Reef "slowly".

not sure if it was the new rock soaking it up at first, or CCA. I slowly brought the levels in line with consistent dosing and testing. 

CCA has exploded in my tank and may have been the culprit. (I never dosed any CCA either)

Again no two situations or tanks are the same.... But food for thought.

Hope this helps as a piece to your puzzle.


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i am not dosing yet. only been up for 8 weeks. ALK is being consumed at a rapid rate and i only have frags... at this point I will have to dose 1dKH a day just to keep it stable. i have the ESV b-ionic bottles on the way

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For me, I have had good success dosing kalkwasser through my ATO. Once I managed to get my parameters to my liking (Alkalinity and Calcium), I would simply add 1 teaspoon to 1 gallon of RODI water in my top off, and it would keep my ALK and CA in check. It also helps boost PH which is a nice bonus. This essentially prevents you from having to purchase a doser or other equipment until you want to make the change. 


Essentially, Kalk is an inexpensive way to keep your ALK and Ca stable. The negative here is that it could cause an issue with your ATO pump in the future and may shorten the lifespan. 


If you find that Kalkwasser isnt meeting your corals consumption, you could then look into adding 2 Part/AFR etc. 


Here is a good read from BRS that explains Kalkwasser in detail.



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On 6/12/2024 at 12:12 PM, anizato said:

P = 2ppb

dKH = 8.1dKH

Ca = 220ppm

I think you may be driving phosphate (P?  ie. PO4?) too low by doing too many water changes.  Stop doing water changes if NO3 gets below 5 ppm or PO4 gets below 0.05 ppm....that's my rule of thumb.  Your levels of N and P were fine back on June 2, but looks like they took a nosedive with all the water changes.


I also think your calcium test kit may be broken.  


What do you get when testing your tap water – and how does that result compare with your water utility's water report?


How do your test results compare if you test the same tank sample three times in a row (ie. in triplicate)?   If there's much variation between results, either you're doing something wrong or the kit is broken somehow.  You should be able to get VERY similar results three times in a row.


IMO do this with your alk test as well, just to be sure.  (I do this every time I start out with a new kit I'm unfamiliar with....and every time I get a test result that doesn't seem like what I expected.)


Also, can you test pH?  How about salinity?   What do you get for both?

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