Lower Alkalinity

[Dwb859]

I'm currently using Tropic Marin Bio-Calcium (also raises alkalinity) to maintain my calcium and alkalinity. The thing I notice with using it is it keeps my calcium spot on yet my alkalinity tends to drop and I have to raise it with a seperate suppplement. What would cause this? If the calcium is raised 5 ppm, the alkalinity will be raised 0.65 dKH, which seems about right. My testing is done with salifert kits, which I find to be really accurate and the results have been confirmed with a backup kit. What is causing my alkalinity to drop faster than my calcium? I maintain an alkalinity of 8.5 dKH and a calcium of 425 ppm. Over the course of a week my calcium stays at 425 by adding Bio-Calcium, yet the the alkalinity wants to drop to around 7.3 dKH or so. Thanks for any advice. :)

[bertoni]

There are a few processes that can consumed alkalinity, but not calcium, and calcifying organisms also consume a bit of magnesium in place of calcium in their skeletons. As long as the shift is gradual, I suspect it's not a problem. This article might help:

http://reefkeeping.com/issues/2004-12/rhf/index.htm

Also, water changes can shift the balance a bit.

[Dwb859]

What a great article. " The following scenarios show what can happen to a reef aquarium whose dosage with a balanced additive system does not match its demand. Alkalinity drops fairly rapidly. After two days, many aquarists might conclude that they need additional alkalinity, when in reality, they need more of both calcium and alkalinity to stabilize the system."

That sounds like my problem.

[Randy Holmes-Farley]

I'd just try a higher dose and see what happens. Unless calcium get's too high, it isn't a concern for it to rise a bit anyway. :)

[Dwb859]

I'm daily dosing the bio-calcium, which is a balance of calcium and alkalinity. My calcium seems to stay at 430 ppm, yet my alkalinity will be be 8.75 one day and 8.0 dkh two days later. If I add more bio-calcium the calcium goes up higher, as well as my alk. I test at the same time each day and add the supplement afterwards. Seems like I'm always having to use another alkalinty supplement to raise it slightly. This works right away but doesn't seem to last. I also feel this is where the white spoting is coming from on my coralline algae. All my corals look great yet my coralline algae has thousands of very small whiteish/purplee spots all over the live rock. My magnesium is at 1320ppm. Any help would be greatly appreciated as I can't understand why I can't maintain the 8.5 dkh on a daily basis if I'm dosing daily.

[Dwb859]

"One of the most common complaints of new aquarists is that their aquaria seem to need more alkalinity than their balanced additive system, such as limewater, is supplying. While there are reasons this may actually be the case over the long term (these will be detailed later in this article), frequently these aquarists are seeing a "chemical mirage" rather than a real excess demand for alkalinity."

This sounds like what could be happening. If this is the case should I just keep doing my daily additions of a balanced additive and see if the alkalinity will return to it's normal level?

[disc1]

"One of the most common complaints of new aquarists is that their aquaria seem to need more alkalinity than their balanced additive system, such as limewater, is supplying. While there are reasons this may actually be the case over the long term (these will be detailed later in this article), frequently these aquarists are seeing a "chemical mirage" rather than a real excess demand for alkalinity."

This sounds like what could be happening. If this is the case should I just keep doing my daily additions of a balanced additive and see if the alkalinity will return to it's normal level?

Almost. You should do like Randy said and up the dose a little and see if you can hold the alkalinity.

[bertoni]

I don't know what the author meant by "a chemical mirage". That doesn't make any sense. If the alkalinity test kit says the level is dropping, either the level is dropping or the kit is faulty. Lots of tanks require more alkalinity than limewater can deliver.

[disc1]

The mirage is that it seems like alk is falling but calcium is staying the same. People see that they've used up 2dkh of alk which seems like a lot and only 14ppm of calcium (if they can even tell that small a difference with their test kit) and assume that they are using more alk than calcium. This leads people to dose the alk without balancing with calcium because they think it isn't falling and they end up in an imbalance. When really all along the calcium was falling in a balanced manner they just couldn't see it as easily as they see the alkalinity falling.

[bertoni]

Ah, now I see. :)

[Dwb859]

Thanks for the replies. I just feel like out of anything I add to my tank I'm always fighting the demon of alkalinity. lol The number seems to change very easy, which bugs me. My alkalinity is 8.3-8.5 dkh and calcium is 430 ppm, magnesium 1320ppm. From what I can tell, my system requires 0.45 dKH daily. I know the bio-calcium is a "balanced additive" could it just be that my system doesn't use calcium and alkalinity exactly to those ratios found in the supplement? The instructions say it will raise the calcium by 28 ppm and 4 dKH.

[bertoni]

The ratio might be slightly different:

http://reefkeeping.com/issues/2004-12/rhf/index.htm

It's also possible that the supplement is slightly off, possibly because of settling during shipping. I wouldn't worry much. I suspect the issue is measurement precision. 1.2 dKH corresponds to about 8.6 ppm of calcium. The Salifert kit drop size is about 8ppm, unless the kit has been changed fairly recently. I think your numbers are within the testing noise limits so far. Maybe I should ask how many weeks have you seen the differential drop, though.

[Dwb859]

I see a small drop after a week. I did recheck my calcium and it was 440ppm. Is the higher calcium contributing to my falling alkalinity? I know if you check a calcium/alk balance chart, a dKH of 8 should have a calcium of around 420 ppm.

[bertoni]

The balance charts have very little meaning. As long as the parameters are in their safe zones, the tank should be fine, and being off from "balanced" has no effect on the consumption ratio. I'm not sure what's going on in your system yet, the drop seems within the acceptable error ranges. To see what's happening, we'd need to have some very accurate measurements from your tank over time, and probably would need to stop any water changes.

[Dwb859]

I keep a log of what I add to the tank. This week I will check the alkalinity several times to see what happens. I'm currently adding Tropic Marin Bio-Calcium, which adds both calcium and alkalinity. I add this daily in small amounts. Do you recommend testing lights on or off? Testing before I add my daily addition or several hours after? I'm using a newer salifert kit to test alkalinity and have been using these test kits for awhile. Thanks for the help

[bertoni]

Lights on or off doesn't matter. I'd just keep the same schedule every day. I'd probably measure the alkalinity just before dosing. That'll reduce any variation due to the supplement taking time to spread.