Brs 2-part: too much Ca?

[pseudorand]

Are alk and Ca always used in the same amounts?

I'm using the BRS two-part, which calls for equal volumes of their Soda Ash and CaCl2 mixes on a daily basis. The theory, per BRS advice, is that alk and Ca are used by the reef in a well-known ratio and their mixes are concentrated such that equal amounts by volume should give you that ratio. But that's not my experience.

I have a 120 with no stony corals yet, but plenty of inverts. I'm dosing 2-part to make sure I've got a handle on my water chemistry before I get LPS/SPS. I'm targing 8.5 dkh and 400-450 Ca. I've kept Alk steady at 8.5 for about a month with 1/3 floz BRS liquid soda ash per day. Supposedly I should be adding the same amount of CaCl2, but when I did at first my Ca went 500+ (above the range of my test kit). So I'm still struggling to figure out how much Ca I should add.

Is the "uses Ca and alk in the same amounts" just a gross oversimplification of reef chemistry that doesn't apply (probably because I have no stony corals yet)?

Will high Ca (475-500) hurt the corals (now in QT) once I get them in my DT?

I know stability is more important than a specific number. Is Ca fluctuating between 400-450 ok? What's range is too big?

And yes, I know I'll need to adjust my routine when the corals go in and as they grow. I buy test kits in bulk when they're on sale

 

[Doctorgori]

I regularly watch Melev (Marc) also and he had a sound byte on high Ca and growth inhibition. Not sure but highly recommend Melev ...
I’ve never gone above 470 and don’t panick at 430
Anyway, I usually only test for Ca bi-monthly or so, so I’d be lying if I said I knew your answer.
Fast growing Clams can jack things up and also make sure you occasionally test your dosers. Any number of things; bad tubes, et can throw calibration off. My BRS dosers are all offa lil.

 

[Randy Holmes-Farley]

I designed that two part, and it matches uptake by corals (ALL corals) as well as abiotic precipitation of calcium carbonate.

But issues like water changes with a mix not matching the tank, accumulating nitrate (depletes alk) use of a sulfur denitrator (depletes alk), or additions you are not aware of (such as alk or calcium in top off water) can skew your demand so that it isn't exactly 1:1. The lower your total daily demand, the more likely these are to be significant.

If you find a slightly different ratio works better long term, that is certainly fine to use.

As noted above, any calcium level from 400 to 550 ppm is fine. There is nothing in the aquarium that will do better at 450 ppm than at 500 ppm.

 

[pseudorand]

I designed that two part,

I love reef2reef! Thanks, Randy.

Sounds like I just do the obvious: test the Ca drop over a few days and dose according, just like I do for Alk. My Ca test isn't so consistently accurate of course, but I'll not worry about it until I get my stories in and they grow past the frag stage.

 

[Randy Holmes-Farley]

I love reef2reef! Thanks, Randy.

Sounds like I just do the obvious: test the Ca drop over a few days and dose according, just like I do for Alk. My Ca test isn't so consistently accurate of course, but I'll not worry about it until I get my stories in and they grow past the frag stage.

That's isn't what I generally recommend, but it a fine thing to do if you do it correctly. Monitor it over at least a week. Calcium kits do not reliably detect calcium changes in a couple of days.