Where is my Calcium going (and should I do anything about it?)

[mythesis]

New 90 gallon tank w/ 20 gallon sump (3 weeks old). Started testing Calcium with API kit and seeing (fast) linear drop. Just trying to understand why it's moving so fast and whether this is something I should address via Reef Fusion 2 part additives.

Current Livestock & Date Installed:​

• 2 Clown Fish (7/21)
• 2 Blood Red Fire Shrimp (7/21)
• 12 Snails (6 Astrea; 6 Nassarius); (7/30)
• 24 Hermit Crabs (7/30)
• Small Duncan Coral Frag (1.5" tall; 1 primary head, 2 smaller emerging) (7/30)
• Small GSP frag (silver dollar sized) (8/1)

Tank Installation:​

~90 pounds of wet live rock (Indonesia; came wrapped in wet newspaper)
~90 pounds of dry large aragonite sand, leaving a rather deep sand bed to my novice eye

Salt​

Using Instant Ocean Sea Salt (Purple box) and mixing to 1.025

Cycle​

Fish were installed a few days after rock/sand. LFS encouraged us to go ahead as the live rock would already have the beneficial bacteria present to support.

Had a small pattern of dark brown junk show up before getting the crabs/snails, which they've quickly dispatched. Seeing small brown spots pop up on back glass / etc, but no large algae breakouts or obvious "uglies" yet.

Question:​

I started tracking the Calcium just to get a more clear picture of what's going on in the tank. I'm surprised to see it drop so quickly given I only have two very small corals in there. Since I'm brand new, figured I should ask about what's going on now so that later on when there's more livestock, I can better understand the processes.

Thanks in advance!

 

[Randy Holmes-Farley]

I expect it is a testing issue.

As an general rule, calcium cannot decline (except by salinity change or water change) without consuming a lot of alk.

A 100 ppm drop in calcium would necessarily consume at least 14 dKH of alk. There is no other way.

Thus, if you are not dosing alkalinity and it is stable, calcium is not actually declining and is likely test error or the effects of water changes or salinity changes..

 

[mythesis]

I expect it is a testing issue.

As an general rule, calcium cannot decline (except by salinity change or water change) without consuming a lot of alk.

A 100 ppm drop in calcium would necessarily consume at least 14 dKH of alk. There is no other way.

Thus, if you are not dosing alkalinity and it is stable, calcium is not actually declining and is likely test error or the effects of water changes or salinity changes..

Ok, thanks. I'll keep testing and see if it finds some stable measurement eventually.

 

[mythesis]

I expect it is a testing issue.

As an general rule, calcium cannot decline (except by salinity change or water change) without consuming a lot of alk.

A 100 ppm drop in calcium would necessarily consume at least 14 dKH of alk. There is no other way.

Thus, if you are not dosing alkalinity and it is stable, calcium is not actually declining and is likely test error or the effects of water changes or salinity changes..

So...my wife just noticed that there's a lot of white covering our rock scape. Is there a chance that we're getting some build up for some reason?

I took a turkey baster and tried to blow it off, and white powder definitely came up. It didn't all leave the rock, though, just some.

I'm mixing my own salt, trying to do about 40 ish gallons at a time and then doing 10 gal water change / week.

Would that be causing an issue?