Plateau in Ca and Alk downtrend??

[Shilpan Patel]

Hey guys just a question about calcium and alkalinity Parameters.

I’m getting into LPS corals now so I’m gonna start dosing. For the last two weeks I’m just dosing and testing and tracking my tanks consumption (it’s 400litres all soft corals currently).

I notice once I get within target range (Alk=9.2, Ca=420), over a week the levels drops very quickly initially and then plateau. The next day they were 8.6 and 410, then next day 8.1 and 390, then two days later 8.1 and 390, then another 3 days later 7.8 and 370.

I repeated the test this week and it had a similar trend.
Do you guys see this often? Th parameters drop quickly in the first few days and then after that they drop much slower?

 

[Ron Reefman]

I have a similar issue and I'm not sure why either.

Lets call for help #ReefSquad

 

[Brew12]

Sounds like a precipitation issue. Soft corals shouldn't have much in the way of Alk and Calc consumption. That would also explain why it is faster at higher alk/calc.
Of course, something other than the corals could be using it such as clams, coralline, snails.....

 

[Flippers4pups]

What is your magnesium level? If very low, it quickly leads to calcium precipitation, thus lowering both calcium and alkalinity.

Aside from magnesium levels, possible testing error.

 

[Atu]

The higher the alkalinity the easier it’s for calcifying organisms to do so. That’s why many SPS tanks run higher alk, like 9-11 dKh.
Also, alkalinity is not only consumed for calcification, carbonate is also used instead of carbon dioxide by many photosynthetic organisms. Coralline can consume a LOT of it.

So what you are observing it’s exactly what someone would expect to observe.

Btw, alkalinity swings is one of the major things to avoid, especially for SPS.

Your consumption will be different at different values of alkalinity.

What you should do to test your consumption is dose everyday X amount (start low) and see where it stabilizes, then if you want a higher value, dose more everyday and check again where it stabilizes.

 

[Bayareareefer18]

I recently had a similar issue. My tank consistently consumes. 5 dkh per day and ca about 3ppm per day. I had about a week or two period where my ca seemed to just not budge at all. After that period seen to resume normal consumption rate

Also curious to hear insight on this

 

[Atu]

If you are interested in understanding what alkalinity is you must read this article by Randy.

https://www.advancedaquarist.com/2002/2/chemistry#section-5

 

[Randy Holmes-Farley Verified Community Expert]

As Atu states, it is normal for consumption to decline as the values drop (and to rise as alk rises).

At some point (alk in the 5-6 dKH range, typically), consumption stops entirely.

 

[Shilpan Patel]

Thank you for your insight everyone this was very interesting!
Yes at one point when I stopped dosing after 2 months my alkalinity just stayed at 5.6.

Thanks for the advice! I was always really worried about testing dosing etc...but I’ve found if you put a bit of effort into it then it all becomes really simple after a while.