Sudden decrease in Calcium/Alkalinity demand

[Brett S]

So I have a 220G reef and I’ve been adding about 180ml each of the BRS calcium and alkalinity supplements daily. (I say about because I have a trident and I’m using trident controlled dosing, so it can raise or lower the amount by about 30% depending on demand).

Oddly, though I started getting alarms on the apex that my calcium and alkalinity was higher than it should be. I tried reducing the dosage, but the trident showed the levels still rising. I wound up turning off my calcium dosing pump entirely a bit more than 24 hours ago and the calcium level didn’t go up at least, but it didn’t go down either, so it appears that I have no calcium demand right now. I’m still operating on a greatly reduced alkalinity dose (about 60ml instead of the 180 that I was adding), but that is keeping things steady, so it looks like there is still at least some alkalinity demand.

My first thought was that something happened with the trident and I was getting bad results, but I just manually tested calcium and alkalinity with salifert test kits and the results were within 10% of my trident readings. I only did one test with salifert so far, so I’ll do another one tomorrow and see if that appears to be trending up or down at all.

My corals (and fish) all look totally fine and my pH level has been stable, so I don’t know what’s going on here. Do you know what might cause a sudden drop in calcium and alkalinity demand like this?

 

[blaxsun]

I would perform a few tests just to rule out testing errors with reagents, etc. If you have an alternate test kit that never hurts, either (or you could bring a water sample into your LFS to have them check the levels).

I've never had my alkalinity and calcium demand just up and drop, though - so I'm at a loss here. Is it possible the last batch of salt you mixed for a water change had higher calcium and alkalinity?

 

[Garf]

I would perform a few tests just to rule out testing errors with reagents, etc. If you have an alternate test kit that never hurts, either (or you could bring a water sample into your LFS to have them check the levels).

I've never had my alkalinity and calcium demand just up and drop, though - so I'm at a loss here. Is it possible the last batch of salt you mixed for a water change had higher calcium and alkalinity?

I have had demand drop to almost zero. I caused it by really making my tank angry. Took 3 or 4 weeks to start consuming again.

 

[blaxsun]

I have had demand drop to almost zero. I caused it by really making my tank angry. Took 3 or 4 weeks to start consuming again.

I've had fluctuations - just nothing earth shattering. I'm sure I've ticked off my corals at one time or the other (maybe just not that much!)

 

[Brett S]

I would perform a few tests just to rule out testing errors with reagents, etc. If you have an alternate test kit that never hurts, either (or you could bring a water sample into your LFS to have them check the levels).

I've never had my alkalinity and calcium demand just up and drop, though - so I'm at a loss here. Is it possible the last batch of salt you mixed for a water change had higher calcium and alkalinity?

The trident checks calcium twice a day and alkalinity 4 times a day, and its results have been consistent, so I don’t think there are testing errors there. As I said, I also tried a manual test with salifert this morning and the results were within 10% of the trident readings. I’ll test with salifert again tomorrow and, of course the trident will continue testing.

I use instant ocean salt and that tends to be pretty consistent (and not super high in calcium and alkalinity). I also have an auto water change that changes about 3 gallons a day in my 220G tank, so even if the levels were super high I don’t think they would be completely cut my need to add supplements. I’ll check the water in my reservoir just to be sure though.

I have had demand drop to almost zero. I caused it by really making my tank angry. Took 3 or 4 weeks to start consuming again.

Weird. I don’t think I did anything to make things angry, but I’ll keep monitoring and see how it goes. I am just hoping that this isn’t a sign of an impending coral die off or anything like that. But like I said, so far, at least, my corals are all looking good.