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View Full Version : Kalk in relation to water volume and demand


Psychographic
10/02/2009, 03:31 PM
I recently added a frag tank to my system. My total volume before was roughly 40 gallons, the frag tank adds about another 20. As of right now I have not added anything that will add to the demand of Ca or Alk, just the additional water volume.

I use a kalk stirrer and have it dialed in for the 40g volume using a timer, will I need to adjust my drip rate to compensate for the extra 20g of water?

I plan to monitor it, but would like to know what I should expect.

bertoni
10/02/2009, 04:04 PM
The extra surface area is likely to lead to more evaporation, thus consuming more limewater. The frag tank might consume a fair amount of calcium and alkalinity, too. I'd expect an upswing in limewater demand. :)

Psychographic
10/02/2009, 05:00 PM
The ATO is seperate from my Kalk, although they share the same reserviour.

The frags that are in the frag tank were moved from my sump so there is no additional frags,,,,,,,,,,,,,,,,,,,,,,,,yet.

tmz
10/02/2009, 10:15 PM
You'll be able to dose more to the larger water volume but if there is no change in demand then why would you need to?

Psychographic
10/03/2009, 07:34 AM
I am asking because I did'nt know how the extra volume would effect my dosing rate as my demand has'nt changed.

I never said I wanted to add more Kalk.

tmz
10/04/2009, 09:24 AM
I don't understand what part of your question has not been answered.

Psychographic
10/04/2009, 10:17 AM
I don't understand what part of your question has not been answered.

These were the 2 replies and I'm a bit confused by the answers.

The extra surface area is likely to lead to more evaporation, thus consuming more limewater. The frag tank might consume a fair amount of calcium and alkalinity, too. I'd expect an upswing in limewater demand. :)

I'm assuming this reply is thinking I dose my kalk through my ATO, as this is the only way it would consume more kalk. As I stated I dose using a timer and it is seperate from my ATO. Also the demand has not changed as there are no additional frags at this point, so that rules out a need for additional kalk based on demand.

You'll be able to dose more to the larger water volume but if there is no change in demand then why would you need to?

When I read this statement, it seems contradictory to me. From what I read out of this, I could add extra kalk due to the extra water volume, which makes sense. The second half of this statement asks why would there be a need if the demand has not risen. This is where I get confused.

Hopefully I can understand this as chemistry is my downfall in this hobby.
Please bear with me, I'm having a hard time trying to explain myself.

If you balance demand, dosing and water volume the way they are, when you increase the water volume, I'm assuming it now will take a larger volume of dosing to saturate the water to the level desired. Which in your reply, "You'll be able to dose more to the larger water volume" make sense.

Seeing as my demand has not changed, I would think the amount of Ca/Alk available to the demand is higher? An example would be a large colony of SPS in a 10g tank would strip the water of Ca faster than it would in a 100g tank.

This is where I get confused as to what the demand to water volume is.

I hope I explained it properly. And yes, the answer may have been given, I'm just still confused by it.

My guess is that as long as the water made for the additional volume is the same in content (Ca/Alk) as the existing water and the demand is still the same, my dosing should'nt at this point need to change.

Thanks for your help.

bertoni
10/04/2009, 06:28 PM
I thought the ATO was kalk. :) I'd expect an upswing in evaporation. If any stony corals are added to the system, I'd expect an upswing in calcium and alkalinity consumption. Sorry for any confusion.

tmz
10/05/2009, 09:40 AM
:fish1: your question is a good one . I hope this helps answer it.

When kalk (lime) is dosed it increases three things: calcium. alkalinity and ph. The ph of fully saturated limewater is about 12.4.

The consumption of the calcium and alkalinity relate to the uptake by corals and other calcifying organisms.Abiotic precipitation when kalk is overdosed also effects it.While the concentration of calcium and alkalinity in ppm would be lower in a larger amount of water,it would be sufficient as long as it remained within acceptable ranges: 7 to 11 dkh for alkalinity and 400ppm or higher for calcium.

The ph effect is related to the overall tank water volume and the amount of CO2 present in it ,as kalk(CaOH)uses the CO2 to make alkalinity,ie, calcium carbonate(CO3) and bicarbonate(HCO3). More water volume will likely hold more CO2. So with an increase in water volume and the same amount of kalk, extra CO2 will form carbonic acid and the tank ph may decline .


In your case.,I would continue the current amount of kalk dosing, test the alkalinity and calcium to insure they remain in acceptable ranges and monitor ph . If anything declines more than you want , you can incrementaly increase the amount of kalk accordingly.

tmz
10/05/2009, 09:55 AM
Afterthought. There may be no decline at all depending on the concentrations of calcium alkalinity and magnesium in your salt mix and the frequency of water changes.

au01st
10/05/2009, 10:25 AM
Keep an eye on the MG level. If you're overdosing the kalk, the MG will drop.

SnowManSnow
10/05/2009, 12:25 PM
Won't it be decided by the number of corals he adds to the system more than just being diluted because of more water volume?

tmz
10/05/2009, 01:16 PM
Won't it be decided by the number of corals he adds to the system more than just being diluted because of more water volume?Depebnds on what you mean by it and wether the new corals and the old are actively precipitating calcium carbonate( growing).

Billybeau1
10/05/2009, 01:28 PM
Keep an eye on the MG level. If you're overdosing the kalk, the MG will drop.

Can you point me to an article that explains that reaction ? I'm not sure I've seen that one. :)

tmz
10/05/2009, 01:52 PM
I don't think I have seen such an article either and was going to question it. However, Mag depletion might occur with precipitation( biotic or abiotic). I think.

bertoni
10/06/2009, 10:40 AM
I think the magnesium depletion issue occurs because limewater adds no magnesium at all, and corals use some magnesium in their skeletons. Also, limewater encourages growth, which will increase magnesium consumption.

GTR
10/06/2009, 03:05 PM
You'll have more surface area for coralline.