What does calcium carbonate precipitation look like?

Oceansize · May 5, 2016

My calcium is high (just above 500) and it hasn't ever created an issue that I'm aware of, however at some point I imagine it's going to start causing calcium carbonate precipitation. I'd like to know how to identify it so I can tell immediately when my calcium has become excessive.

As long as I'm on the subject, I've also noticed that my coral and coralline algae do better when my alk is around 11 instead of 7, even though my tank is ULNS. I've been under the impression that Alk should be closer to 7 in a ULNS tank, but my experience seems to contradict this popular conclusion. What are the dangers of having high Alk in a ULNS tank?

Also, because I am running both a sulphur denitrator and a calcium reactor, my pH is on the low side at 7.9, but it is very stable. Should I be concerned long-term?

twilliard · May 5, 2016

It's a white powder coating on everything

Oceansize · May 5, 2016

twilliard said:
It's a white powder coating on everything

Does it encrust or does it blow off like dust?

KingBlingTX · May 5, 2016

I'm not sure about the water where you live, but the water where I live is notorious for leaving what is commonly called "scale" on dishes, shower/tub tiles & glass. If you've ever seen this whitish hard water deposit on glasses coming out of the dishwasher, you've seen calcium carbonate precipitate.

Oceansize · May 6, 2016

Well I'm familiar with the effects of hard water but I assume that scale forms only when the water containing the precipitate dries out. When it occurs in a SW aquarium, is it as hard to remove as scale on the glasses in the dishwasher?

Randy Holmes-Farley · May 6, 2016

High calcium is not usually a primary cause of precipitation. Doubling calcium from 420 to 840 ppm is only the same with respect to precipitation as pH going up by 0.3 pH units or so, or alk going from 7 to 14 dKH.

I discuss precipitation in great detail (with pictures) here:

What is that Precipitate in My Reef Aquarium? by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2005-07/rhf/index.htm

Oceansize · May 6, 2016

Randy Holmes-Farley said:
High calcium is not usually a primary cause of precipitation. Doubling calcium from 420 to 840 ppm is only the same with respect to precipitation as pH going up by 0.3 pH units or so, or alk going from 7 to 14 dKH.

I discuss precipitation in great detail (with pictures) here:

What is that Precipitate in My Reef Aquarium? by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2005-07/rhf/index.htm

Thanks Randy. My Calcium is just north of 500, while my Alk is 11 and my pH is 7.9 in a ULNS system. Do you see a cause for concern here? I ask because I seem to recall you telling me in the past that Calcium could become a concern once it gets comfortably into the 500's, and also that ULNS should not have Alk that high. And I also wonder if 7.9 pH is just a touch too low for a tank with Alk of 11.

Randy Holmes-Farley · May 8, 2016

Oceansize said:
Thanks Randy. My Calcium is just north of 500, while my Alk is 11 and my pH is 7.9 in a ULNS system. Do you see a cause for concern here? I ask because I seem to recall you telling me in the past that Calcium could become a concern once it gets comfortably into the 500's, and also that ULNS should not have Alk that high. And I also wonder if 7.9 pH is just a touch too low for a tank with Alk of 11.

Nope, no particular concern. The pH is fine.