sudden drop of Ca level

mrtian97 · Apr 28, 2017

My reef tank is 90 gallon total water volume, setup almost 1 yr, all corals are doing great, growing including sps. WC 10 gallon/wk with Redsea coral pro, use kalk for ATO, and dose soda ash (125mL/day with auto doser ) and 95mL/day of Ca using 2 parts recipe (and 7mL of Mg). parameters been stable alk 8.2, Mg 1400 and Ca 425, pH 8.3.
this wk I tested my Ca dropped to 360, I don't know for how long as I don't test Ca regularly (maybe 2 wks ). All corals are still doing great, tested 2x and tested again today, still low (using Red Sea test kit).

I increased the dose by 30mL per day (seems equal to 6ppm) and today I added another 30mL since it's still about 370 ppm

Any suggestions of reasons of sudden drop of Ca level?

Thanks

Zoarium · Apr 28, 2017

What test kit are you using and is it expired?

Dr. Reef · Apr 28, 2017

i suspect the kit, maybe its expired or gone bad. can you check with another kit or maybe take a sample to lfs or fellow reefer. if it still comes back low then it could be 2 things. 1. saltmix may be low (which happens every now and then) shake the salt or bucket, roll it around a little. or 2. it could be that doser is not dosing properly or maybe clogged.
3. maybe your tank has gone up on cal consumption

Randy Holmes-Farley · Apr 28, 2017

I also suspect the test. Calcium cannot decline (except by water change with a very low calcium mix) without alk also dropping.

A drop of 65 ppm would be accompanied by about a 10 dKH drop in alk (or the demand for an extra 10 dKH of alk added) . If you did not observe that, then it is testing error.

mrtian97 · Apr 28, 2017

Thanks guys

mrtian97 · Apr 28, 2017

I use red sea test kit, expiration 2019. I will check with others

mrtian97 · Apr 29, 2017

unfortunately it's not the test kit, I made saltwater for my regular weekly WC, I tested that water and I got Ca 450 (range should be 455-475 (RS Coral Pro). I increased my daily dose by 60mL and I don't see changes in my level of 370.

Next would be replacing my Ca mix for dosing, I am using the CaCl for ice melter, I believe ahould be 2.5 cup for 1 gallon (following Randy 2 parts recipe).

Any thoughts? my corals are doing fine, no difference but I don't want to stay at 370 level

Thanks

Randy Holmes-Farley · Apr 29, 2017

How do you know it wasn't the kit?

But regardless, calcium values are not critical, so no matter what it really is, boosting it by 50 ppm over a couple of days wouldn't hurt anything.

mrtian97 · Apr 29, 2017

Thanks Randy, I figure it wasn't the test kit bc I use the same test kit to test my newly mixed saltwater and the test showing 450 which is close the labeled of 455-475.

The Calcium mixed is a new batch that I made recently, maybe I did not used 2.5 cups when I mixed it