Calcium too low?

DoomervilleG · Aug 13, 2021

Hello

About a month ago, I added a duncan frag to our tank. It is our first LPS, and its doing quite awesome I might add. (Proud moment after two weeks of it being closed

). However, some of the numbers on this mornings test are a little wonky, and I did them twice. My question here is, I know that LPS will take calcium from the water to build its skeleton, but how much does a single LPS take out in a week?

Numbers: 8/6/21
Cal: 440
dKH: 11 (KH: 196)
Nitrate: 20ppm (Trying to get it lower to around 10)
Nitrite: 0
Am: 0
Phos .25 (Battling this one down, still)
PH: 8.0
No magnesium test yet.

Numbers: 8/13/21
Cal: 380 (Ran test twice)
Same numbers as above
Magnesium test has not arrived yet.

The tank has remained relatively stable since set up, with calcium at a solid 440 every week. I expected it to drop a little, due to the duncan, I did not expect it to drop as much as it appears it has, but I'm brand new to the hobby, so.

All of my current tests are API, though I have some Red Sea kits ordered, just awaiting delivery.

Everything in the tank is mega happy, except GSP, but I suspect that is a flow issue as I moved a powerhead to accommodate the duncan.

I'm using Fritz RPM salt mix and have since I started the tank 7 months ago, weekly water changes (Today is water change day).
While I'm not extremely concerned, as everything is happy, I'm genuinely curious as to when I'll have to start dosing, if at all.

This is a 32g biocube with skimmer and filer floss.

Evo R · Aug 13, 2021

I would strongly suggest getting a quality Magnesium titration test kit. I personally prefer the AF one. Without knowing what your Magnesium levels are you are not getting the full picture.

Studies have shown that Magnesium shortage/depletion rates negatively impacts Calcium uptake ect. And LPS thrive in slightly higher Magnesium levels.
Your water volume is small, so a drop from 440 to 380 in a week might seem huge to you, but in a Eg: 120 gal system a drop from 440 to 420 might seem insignificant....and manageable with weekly water changes alone.

Look on the plus side.....your LPS is using the Ca which means its gowning. If all goes well and everything remains stable, you might see a new head in the near future.

Evo R · Aug 13, 2021

PS.

Good rule of thumb, only start dosing when water changes alone cant keep up anymore.
And never ever ever ever dose what you can not test for!!!! That's asking for trouble!

And what other corals etc. do you have in your tank? Remember that all corals use all of the elements to grow and survive to some extent.

Randy Holmes-Farley · Aug 13, 2021

If alkalinity is not declining, it is unlikely that calcium is actually declining. For calcium to decline by the reported 60 ppm requires a drop (or addition) of at least 8 dKH of alkalinity.

DoomervilleG · Aug 13, 2021

Evo R said:
PS.

Good rule of thumb, only start dosing when water changes alone cant keep up anymore.
And never ever ever ever dose what you can not test for!!!! That's asking for trouble!

And what other corals etc. do you have in your tank? Remember that all corals use all of the elements to grow and survive to some extent.

I have a purple frilly gorg, 2 small zoanid colonies (7-9 heads each), a ricordea and some gsp for additional coral.

Randy Holmes-Farley said:
If alkalinity is not declining, it is unlikely that calcium is actually declining. For calcium to decline by the reported 60 ppm requires a drop (or addition) of at least 8 dKH of alkalinity.

That was my assumption from everything that I had read, which is why I thought the calcium reading 380 odd, with no ALK drop I ordered a whole suite of tests by Red Sea, but those haven't arrived yet (Couple days late).