Capabilities of Kalkwasser

Many people may not realize just how much calcium and alkalinity are packed into kalkwasser.  I found this graph by Craig Bingham that shows just how much can be delivered:

The colored fan shaped areas are calcification rates in kg/m2/yr.  A "typical" ocean reef is somewhere between 3 - 6 kg/m2/yr.  Bingham claims that some tanks can be as high as 20 kg/m2/yr (which I'd probably have to see to believe).  I calculated the calcification rate on my little 20 gallon tank about 6 months ago at 2 kg/m2/yr... low end for sure, but I don't have many sps.  Back to the graph:  My 125 gallon tank evaporates 4 gallons per day, with a surface area of .84 m2 (6' x 1.5') I could theoretically support 15 kg/yr of calcification using just kalkwasser.  That's over 30 lbs of coral growth in a year!

The actual amount of kalkwasser that can be added is set by evaporation rate and tank pH.  The most you can add is equal to your evaporation rate.  If you add too fast or too much, your pH can get very high which can lead to a crash of existing calcium and alkalinity and/or harm to tank inhabitants.  How can kalkwasser additions be maximized?  Gas exchange is the key.  Here are the desirable reactions that take place:

Ca(OH)2 = Ca + 2 OH      (dissoving of kalkwasser)

The OH as hydroxide ion is not of any real use.  This is what causes the pH of the tank water to increase.  But CO2 is our friend and comes to the rescue:

OH + CO2 = HCO3  (and)
OH + HCO3 = CO3 + H2O

With the addition of CO2,  the two OH ions are changed to a carbonate ion (CO3) and a water molecule.  So each molecule of kalkwasser becomes one molecule of calcium and one molecule of carbonate... a balanced additive!

Again the key to maximizing kalk additions is to maximize CO2 contact.  Lots of aeration, big skimmer, fans and water motion!  Do all this and still keep the pH below 8.4.

Thats sweet i am getting in alot of Kalkwasser this week thanks John.

Are you familiar with how reactors work Jon? Have you ever used one? They are tricky little buggers. If the effluient falls from 6" above the water line into the water, would the carbon dioxide release into the air? Or is it saturated into the solution? Where would you start your drip & flow rates on a reactor? Maybe we could talk about this on another thread if you don't want this thread to change directions.

I'm sure that some tanks could grow 30# of growth in a year, but they are probably 2000+ gallons in Germany somewhere.

If the effluient falls from 6" above the water line into the water, would the carbon dioxide release into the air? Or is it saturated into the solution?

No, I would say you don't want the CO2 to leave at that point.  There is only so much calcium and carbonate that can stay dissolved in water.  The lower the pH the more you can have and vice versa (the higher the pH the less you can).  The CO2 in the reactor reduces the pH down to the mid 6s causing CaCO3 to dissolve.  If you were to remove all that excess CO2 I think some of your calcium that you just dissoved would precipitate as solid CaCO3.  You want the reactor effluent to mix with your tank water first then degass the excess CO2, imo.

I mean Jon.........

No problem, I've been called much worse.

Thanks Jon. That answered my questions.

Sounds like a deal to me! I'll be sure to get some. Is it the same brand as the other chemicals that you got?

Marcus wrote: Where would you start your drip & flow rates on a reactor?

It's my understanding that the manufacturer of the reactor will give a minimum drip rate and a minimum bubble per minute rate and then you go up from there.  Somewhere around 40 drips per minute of effluent water and 10 bubbles per minute of CO2.

Also, in the Sea Star Online, April 2001 article about Ca Reactors by Jim Perry.  He mentions dripping into the intake of the skimmer.  Would this work ok? 

 

 

 

Edited by Travis

Jon -
You evaporate 4 gallons daily? I also have a 120 gallon tank and I only loose about 1 gallon per day.

I covered my sump (55 gallon) with acrylic. That cut down the evap rate significantly. But, like I've said earlier, I can't add kalkwasser quickly enough to keep up with my tank ...

You evaporate 4 gallons daily?

yup, that's rediculous ain't it?  I use almost a full 5 gallon container daily.  It's becoming a hassle carrying those totes around, I'm looking for an RO unit.

Shane and Travis, what became the bottleneck?  Evaporation rate or pH?

Jon - I can hardly believe your evaporating 4 gal. a day. I evaporate around 1 gal. a day in my 150, it seems to increase though during the winter time.

I forget - what lighting do you have?