I know there's a thread on this in the sponsor forum.....

[ReefinChicago]

......but I wondering if anyone else is seeing RC with low alk/calc numbers.

As I posted on the 22 thread, I started testing for calc a few weeks ago, and found that it was around 320. Alk was good. I dosed one part calc and got it up to 400-420 over a period of a couple weeks. Then, after doing a water change this weekend, saw the number drop back down to 380. I then tested the 30, which has had nothing in it except for snails, and the calc was at 320-340.

So, I tested a batch of water I mixed yesterday. SG 1.026, calc 340, alk 9.

I'm using API kits. Ordering some Red Seas today, since I need to replace the APIs anyway. So I'm wondering if anyone else has seen this. Like I said, there's been some stuff in the sponsor section, but haven't seen anything in here, at least for a few months. Wondering if it's my kits, or the water, or the way I'm mixing the water, or if I'm doing something else wrong.

 

[ReefWreak]

I'd probably first blame the "something else" category. Usually it's old salt that has been open a long time, user error, mis-calibrated salinity measurement throwing off metrics. Then it usually goes to testing kits. API alkalinity kits are supposed to be good, but I've never heard about their calcium kits.

I use Salifert for everything, and they're pretty consistently pretty good and pretty inexpensive. For me, API kits are perfect for first dipping your toes into the hobby. Once you really start to care about calcium and alkalinity, you move to another brand for those kits.

It's possible that the salt is off, but there's usually a big uproar if there is a batch of salt with wrong numbers. No salt is perfect, but it just doesn't happen that often any more. If it did happen more often, it wouldn't really show up in the nano section, but you better believe it would be in the first two to three pages of the Reef Chemistry or General forums here on RC, since a LOT of people use RC.

My thoughts? Check for precipitation on the bottom of the mixing vessel. I know I had that problem for a while as well.

 

[ReefinChicago]

Will do, thanks.

Will do, thanks.

I'm figuring it's something with me, so that'll be a good place to look.

 

[DustanT]

My calc was low this last batch, 420 with fresh mix. Maybe time to switch from reef crystals idk.

 

[ReefWreak]

My calc was low this last batch, 420 with fresh mix. Maybe time to switch from reef crystals idk.

For what it is worth, 420 calcium is good, and matches oceanic calcium levels perfectly. The matching balanced alkalinity for this is right around 8.0-8.5 dkh. (which oddly enough is higher than oceanic levels, which are around 7.0dkh, but I guess biological activity suppresses the alkalinity buffer a bit?).

Some light reading that would be helpful is ReefKeeping magazine's article on optimal aquarium parameters or this one which is a bit more detailed and complicated, also in reefkeeping magazine.

If you haven't checked it out yet, reefkeeping magazine is a wealth of excellent information, particularly on chemistry.

 

[ReefinChicago]

Just an update to this.....

Just an update to this.....

......and a learning moment for me.

I had to travel for business this week. Left Tuesday, got back yesterday. On Tuesday morning I tested calc, and it was 380. I added some reef calc, so as of then it should've been 420 or so.

This morning I did my weekly water change. I make the water up after I change each week, so I'd made this batch last Sunday. Instead of just using the water as is I moved the powerhead around a bit to 're-mix' the water, and did the change. Tested the calc, and it was 420.

So I suspect, as Reef said, that I had some calc precipitate out of the water at the bottom of the bucket.