I am baffled...Alk, Ca, Mg

[jb61264]

I have a 75g SPS dominant reef. I run a Reef Octopus single chamber calcium reactor and am at a loss recently on some water chemistry tests I did.

To tell the whole story, I sorta let things go on "auto-pilot" for the past couple months. A couple weeks ago I noticed a couple corals slowly start bleaching a little so immediately did some tests. I have Hanna Checkers for Alk and Ca...I use Elos for Mg.

So a couple weeks ago I started testing and got Alk=6.1 and Ca=383
I decided to drip a 1/2 gallon of Kalk...next day I was Alk=6.44 and Ca=392

I do this for a few days and on 8/11 I am at Alk=8.1 and Ca=388
I drip 1/2 gallon ok Kalk every other day (with my CaRx going)

On 8/24 I test Alk=6.78, Ca=402, Mg=1200
On 8/26 I test Alk=7.28, Ca=455, Mg=1150

Just for fun on 8/24
I test the effluent from my CaRx...Alk=13.7, Ca=468
I test the kalk that I am supplementing...Alk=16.8, Ca=547

I am a bit baffled as it doesn't seem like I can "catch up" to what my tank is demanding. The calcium reactor I have should be sufficient. I am using ARM extra course media and had filled the reactor up a few months ago and it is still about half full.

I'd like to get my params a little more normalized like, Alk=9, Ca=420, Mg=1300

Any suggestions or recommendations or explanations?..lol

One thing I should also point out...my pH has been swinging low for a while, it will get down to 7.8 and night and up to 8.0 during the day, even though I run my sump with chaeto light on alternating cycle and when i have been dripping kalk it is overnight as well. I dialed back my CaRx a bit on the drip rate as I thought this might be contributing to the lower pH.

[bertoni]

I suspect the reactor just needs to be tuned up. A second chamber might help with the pH drop. You could consider dosing a 2-part, for that matter.

For the time being, I'd dose the alkalinity up to at least 7 every day. If you test and then dose at the same time, you should be able to get a trend line going. I'd dose baking soda, personally. At some point, you'll need to dose calcium as well. You could start now, or do that later.

[bnumair]

cal reactor should be tuned in to meet alk demand. and for starters it should have an output of 3 times ur number of alk u want to keep. so if u want an alk of 8 u need to tune is around where the out put of reactor is around 24. then fine tune as needed.