pH, calcium and kalkwasser in a nano tank

[Gribbles]

Hello,

I'm having difficulty keeping my pH in a good range. Today my minimum was 7.71 and maximum 7.95.

Tank is a 20g cube aio, waterbox.

My tank also doesn't consume much alk or calcium. Roughly .2 dkh per day and about 10ppm calcium per week. I test these with hanna checkers.

Would this be a good opportunity for kalkwasser? I assume not because of the calcium uptake. Any suggestions otherwise?

 

[arking_mark]

Ca and Alk are almost consumed equally in a tank ( ignoring NO3 effects).

At 0.2dKH per day, you'll see roughly a 7ppm decrease in Ca every 5 days (basically 7ppm per 1dKH).

Most test kits are at best +/-20ppm...I have found them closer to +/- 10%.

So to see a Ca drop, you may need to wait a couple of weeks.

So basically, I would use your Alk measurements for balanced dosing. Kalkwasser is excellent for this and has a nice pH bump side effect.

As to your 7.7 pH reading...you may have an aeration, CO2, or measurement issue. I'd do a cup aeration test...many low readings are fixed by aeration or understanding the limitations of our test kit and probes...many of which are +/-0.2 accuracy.

 

[Gribbles]

My concern is that dosing kalkwasser (calcium hydroxide) to achieve a desired dkh or ph level, it would increase my calcium much more than my tank needs.

Am I off base here?

Regarding your comments on aeration, I have indeed had issues with my protein skimmer's pump and am in the process of getting a new pump on warranty. I do have my return pump angled to greatly disrupt the surface, though.

Edit: The skimmer works, mostly, I just have to check the impeller several times a day.

 

[arking_mark]

Yes. You are off base. Ca/Alk consumption is almost equal...so balanced dosing works well.

The actual inbalance comes from CaCO3 surface poisoning from mostly PO4 and Magnesium which is dependent on your tank stocking.

I use an ICP test to adjust Ca every 6 months or so.

 

[Randy Holmes-Farley]

I don’t think that kalkwasser will be particularly useful for boosting pH over the course of 24 h if you only need 0.2 dKH of alk per day. The boost from adding that all at once will be only about 0.1 pH unit, and it will drop back pretty quick.

if pH is really that low in such a tank, you may need to look for fresher air to the room.

 

[Gribbles]

I don’t think that kalkwasser will be particularly useful for boosting pH over the course of 24 h if you only need 0.2 dKH of alk per day. The boost from adding that all at once will be only about 0.1 pH unit, and it will drop back pretty quick.

if pH is really that low in such a tank, you may need to look for fresher air to the room.

Not the answer I wanted to hear, but perhaps the one I need.

Thanks Randy, happy reefing.

 

[arking_mark]

Not the answer I wanted to hear, but perhaps the one I need.

Thanks Randy, happy reefing.

One thing to note is that as you increase pH you increase Alk/Ca consumption through increased biological consumption and abiotic precipitation. So you may find that kalkwasser dosing will increase consumption and increase kalkwasser demand...

 

[Gribbles]

I was wondering that same thing actually, but doesn't the ph boost from kalk (and soda carbonate for that matter) last only a short time?

I dosed soda carbonate this morning, got a .06pH boost for roughly an hour or so.

 

[arking_mark]

Typically speaking kalkwasser dosing is limited to your evaporation rate which is usually somewhere around 1%. At 1%, fully saturated kalkwasser only provides roughly 1dKH to your tank. I found that a continous drip at evaporation rate gave me around a 0.1 pH boost. Spiking the tank had a larger initial pH increase but was short lived and not the stability I was looking for.

 

[Gribbles]

Typically speaking kalkwasser dosing is limited to your evaporation rate which is usually somewhere around 1%. At 1%, fully saturated kalkwasser only provides roughly 1dKH to your tank. I found that a continous drip at evaporation rate gave me around a 0.1 pH boost. Spiking the tank had a larger initial pH increase but was short lived and not the stability I was looking for.

A .1 boost would be fantastic. I've been reading about kalkwasser these past few days in my free time (what's left of it...) Looks like I need to keep reading.

So if it is tied to your evaporation rate, can you just fill up your ato with it?

 

[Randy Holmes-Farley]

A .1 boost would be fantastic. I've been reading about kalkwasser these past few days in my free time (what's left of it...) Looks like I need to keep reading.

So if it is tied to your evaporation rate, can you just fill up your ato with it?

The problem is your 0.2 dKH per day of demand. You'll overshoot that and alk will rise.

Demand may rise as pH rises, but likely not not enough to allow you to deliver 1 dKH per day.

 

[arking_mark]

A .1 boost would be fantastic. I've been reading about kalkwasser these past few days in my free time (what's left of it...) Looks like I need to keep reading.

So if it is tied to your evaporation rate, can you just fill up your ato with it?

A couple of things:

1. Only dose based on your Alk consumption and NOT pH as that can result in Alk instability and CaCO3 precipitation events
2. ATO based kalkwasser dosing is NOT a best practice and can result in inconsistent dosing and is prone to overdosing and instability
3. Best method is a slow drip or incremental dosing throughout the day that replaces actual daily Alk consumption.

 

[Gribbles]

I need to dose alk in some form, obviously. Is there any reason to dose sodium carbonate instead of kalk? I know that question is a little ambiguous and leading, sorry about that. Cost? Hassle?

Randy, are you suggesting that dosing kalk wouldn't matter (or make why difference) in my situation?

Thank you both for taking the time answering my questions, by the way.

 

[Randy Holmes-Farley]

I’m suggesting the alk method won’t matter much, but hydroxide (kalkwasser is one way to dose hydroxide) always has the highest pH boost and it’s fine to use. Just dose whatever you dose based on alk measurement, not pH.

 

[Gribbles]

Fair enough, thanks!