Constantly fighting to keep my Ca up
 

I have a 90 gallon mixed reef that has been going for over 4 years. In the last few months I have been struggling to keep my Ca above 380. My Mg was low too, but has since become stable again at about 1400. I started adding kalk a month ago which has decreased my dosing but my ca keeps dropping still. I am using C-balance to dose and am dosing them equal. Right now my Ca is 380 and my alk is 8.4 which is fine except that if I just leave it, it will drop to 350 over a period of time. I had the ca to 410 from a water change last week but now it is 380 even though I am dosing. I have read Randy's info but it doesn't say how to get the ca up and keep it there.

Have you checked your water with someone else's test kits/different brands of kits?
Wouldn't hurt to make sure your test results are accurate.

I've never dosed Kalk, so no help here. But I'm surprised to hear that your Ca is dropping when your Alk isn't, and that you can't keep your Ca up when your Alk is.
Maybe it's due to the amount you dose of Ca not being fully integrated/absorbed by your water when you test ???

Maybe wait a bit longer after you dose before you test your Ca.
I usually wait at least an hour, if I test after dosing at all.

Keep in mind that when you dose either Alk or Ca, they play off each other and may see-saw their levels when they mix.

Hope I explained myself correctly and accurately ...

Good luck.

You may want to check your Mag level apparently if it's not right it affects both Ca & alk. from what I understand.

She should be good to go

Yes, I have checked with 2 different brands of test kits that are both new-Salifert and Red Sea. I discovered awhile ago that Salifert is not that accurate for alk. It measures high but the ca kits both say the same. I dose them an hour apart and have been doing it for a couple of years. When I get my ca to go up, I stop dosing alk. My tank is very full of coral and I've got a lot more sps now so not sure if that is why this is happening.

I was dosing over 100ml/day each of Alk and Ca with 2-part before my tank failure and had full growth of SPS, if that helps.
Maybe your tank is just using huge amounts of product ?

Yah, I was so sorry to hear about your tank crash! Really sucks. On the bright side, now you get to redo your tank! There are things I would certainly do different if I had a new tank!
My dosing has dropped a lot since I started using kalk. My alk is stable and I have no problem keeping it up. And now I just read on Randy Holmes site that lower ph should allow for keeping the ca and alk up even easier. I think that I need a chemistry person! My ph is about 8.2 during the day and is dropping to about 7.8 at night. Maybe that has something to do with my issue?

That's pretty common and not directly linked to Ca. It's more of a dissolved oxygen/co2 relationship.

Can you get your hands on some Calcium Chloride locally ? Maybe one of us out your way can get you some ?
All you need right now is 2 cups to mix with RO for a total of 3,785ml. Don't add it to a gallon, but rather mix it 'till dissolved in about 1/2 gallon, then add enough RO to make a gallon.
Once you have that gallon mixed, use this online calculator to help with the dosing amount needed.

My thought is to use the chloride to get your calcium up, and then carry on with what you've been doing to maintain the big 3.

I've never used Kalk or C-Balance and don't want to lead you in the wrong direction, so hopefully someone who has will speak up ...

Not sure I get what you mean here.
Keep maintaing alk, but add extra ca. Once balanced they should stay that way.
Your tank will use something like 10 times alk to ca, so be sure you are dosing in correct volumes as per product instructions.