Where does all the calc go?

[drhyed]

I have a fairly lightly stocked soft/lps 75gal tank and I check the calc/alk/mag usually every 4-5 days and without adding any new corral calc went from 430ppm to 160ppm in 5 days, Ive had drops of 80-100ppm but never a drop like this, I thought it was the test kit but my spare new kit resulted in the same result. I have new zoa's poping up all over, would they be sucking up the calc?

[blanden.adam]

No. Zoas don't use calcium, and after the calcium drops that low corals can't use it anymore -- too hard to suck it out of solution. What's your alkalinity like over those days? And how many times have you observed this?

In truth, it has to be a testing artifact. Even if you had an alkalinity of 10 dKH, and precipitated all of it out of solution with calcium, your calcium would be 360ppm (7 ppm calcium per 1 dKH alk). So, it can't be consumption/precipitation. I'd just order a new test kit, or repeat the test, or get someone else to test it, because it really can't be anything else :).

[bertoni]

I agree that those results seem off, unless you were dosing a lot of alkalinity and no calcium at all. Coralline can consume a lot of calcium and alkalinity, but that's still a large drop.

[drhyed]

Alk was 7.8, ph 8.0 so I wont panic or dose like crazy until I test with a new kit. I appreciate the help!

[Reef Noob]

What were the actual levels this time and last time? It is the Magnesium that allows the calcium to super saturate. When the magnesium is low, the calcium will precipitate out rather quickly.

[Reef Noob]

Here's a chemistry log with parameters if it will help.
http://floridareefaquariumgroup.com/showthread.php?268-Free-Reef-Log

[drhyed]

Thanks! Im going to test again tonight with a new kit and see what numbers I get, I dont have the mag number in front of me but it was in the 1100's

[greyreef]

Quite possible some of the drop is your low mg
Do you have calcium depositing on your equipment?
Might need to raise your Mg to raise your ca!

[bertoni]

Magnesium at 1100 ppm is fine. I ran tanks at that level for years because that was the level that Instant Ocean provided out of the bag. The canonical average is 1275 ppm or so, and that's what I eventually started targeting just to try to match natural seawater.

[BearCatFish]

Subscribed just to see what the new test kit gives you & to see what the problem is.