Maintaining Calcium and Alkalinity

[Alan]

There are many ways of maintaining CA and ALK in a system, recently i switched of my reactor for a few reasons. One of them being it could not keep up with the demand of the system and i did not feel that i had proper control and my PH was starting to run on the low side because i was pushing the reactor harder and harder.
Anyway swapped over to Calcium chloride and Bicarb, both purchased at the chemist as on a big system it would cost an absolute fortune to use branded products. I now had control of both CA and ALK and could determine what i wanted them at. I raised my ALK to 8dkh and my CA at 390. To maintain these levels i was using 6tsp of bicarb and 7tsp of calcium chloride a night. I started to worry about the amount of chloride i was adding to the system, but at the end of the day all the corals looked happy.
I then spoke to AC and he suggested i use the kalk slurry method, which i have now been using for a week and have been very impressed with the results. I still add the bicarb daily but now add 1.5 tsp of calcium hydroxide every evening. This has raised my ph to the 8.3 level, kept my ca at 400 and is fairly constant with very little swing except when i add the slurry. I have noticed a marked increase in the growth tips on my birds nest and my large clam which has seemed to slow down in growth over the past few months, has suddenly picked up the growth rate again. These are the 2 bits of live stock i usually watch to gauge the health of my system.
All i can say is all the above methods do work very well, you will have to be cautious when using kalk what ever form you choose to use it in. The only draw back to dosing manually is when you go away on holiday........who do you trust to do the dosing.

 

[viper357]

Nice to see you having success Alan.

How exactly does the slurry method work, do you simply mix the kalk and RO and then just pour the milky solution into your sump?

 

[palmerc]

Hi Alan,

Are you only using the 1.5 tsp of kalk powder now or are you still using calcium chloride as well.

If only the kalk powder I am concerned that you may not be adding enough calcium. There is a hell of a lot more calcium in 7 tsp of Calcium Chloride (about 9500ppm) than in 1.5 teaspoons of kalk powder (about 2500ppm).

Clinton

 

[Adam]

Alan

Tell us about this slurry method

 

[Alan]

Hi Alan,

Are you only using the 1.5 tsp of kalk powder now or are you still using calcium chloride as well.

If only the kalk powder I am concerned that you may not be adding enough calcium. There is a hell of a lot more calcium in 7 tsp of Calcium Chloride (about 9500ppm) than in 1.5 teaspoons of kalk powder (about 2500ppm).

Clinton

I hear you here Clinton but i started off rather low and am busy building my way up as i did not want to over dose the system, will check the Ca levels in the next couple of days and see which way they are going and then adjust the dosage until i can get a point where it is stable.
Adam all i do for the slurry is mix the Calcium Hydroxide into a cup of cold water and slowly pour into the display infront of a strong pump at night. The general idea is the ph should not rise by more than 2/10's of a point after half an hour. You do get an initial spike but it then settles.

 

[Marius--]

Hi can i ask a noob question. Almost 1 year in the hobby, Is there a way to maintain alk levels automaticly Without doing testing and adding stuff manualy.

 

[palmerc]

Hi can i ask a noob question. Almost 1 year in the hobby, Is there a way to maintain alk levels automaticly Without doing testing and adding stuff manualy.

You could use a micro-dosing pump, but you would still need to check your alkalinity quite regularly (at least in the beginning) to ensure you had the correct dosing rate.

Alternatively if you have an auto-top off add your weeks (or however long your top-off water resevoir lasts before being refilled) buffer requirement into this. You would still need to test occasionally to ensure everything was OK

 

[Marius--]

Ok so what does a kalk reactor do

 

[TheWaterboy]

great stuff. i too have decided to not use a calcium reactor on my new system, for differant reasons, but am glad that i will still be able to maintain levels as this was my concern when deciding....thanks alan......informative thread

 

[palmerc]

It doses kalkwasser (calcium hydroxide). Basically it is an auto-topoff with the water running through the kalk reactor first. This adds alkalinity and calcium. I answered the question before this based on just maintaining alkalinity alone.

 

[Marius--]

ok thanks palmerc

 

[Alan]

The big problem with a kalk reactor is it very much depends on your evaporation rate. If you don't evaporate enough water you are not going to get enough kalk into the system. Similarly if your calcium/alk demand is too high with plenty stony corals i do not believe a kalk reactor will keep up, it will have to be used in conjunction with a calcium reactor.

 

[Mo_G]

Interesting, will wait for the results.

 

[TheWaterboy]

alan, i hear you, but my circumstances are somewhat differant to yours. do you think the following would work....
i will not be keeping much SPS.....maybe 1 or two MONTI's....., i also will be running open top so i am expecting some evaporation, aswell as i will be doing good 30 - 40 % synthetic salt water changes weekly......... , that should compensate....if not well i have plenty calcium and buffer supplements i could add......
my reason for not using a calcium reactor is leaning greatly on a limited space problem......i do have space but it will be really cramped if i install, aswell as it takes a few breakers on my db box.....you know how it goes.....reactor, controller, solinoid etc etc....next thing the db looks like spaghetti junction.....lol

anyway, get off that lazy butt of yours and come help me design the stand and sump so i can give it to chris to manufacture

 

[Alan]

Sounds fine Marco, sorry just been fairly busy this week, half my staff are off with flu so have been running around a bit. Hell yesterday i even played driver to one of my crews.

 

[Alan]

okay here is a question for our chemists. Does Kalk add buffer and Calcium together or is it mainly calcium?

 

[Midasblenny]

okay here is a question for our chemists. Does Kalk add buffer and Calcium together or is it mainly calcium?

Yes alan, there is a calcium ion and a hydroxide ion in calcium hydroxide which aids in the formation of carbonates and therefore assists in the buffering process.

 

[Alan]

When you say assists does it actually add buffer or assist by neutralising acid in the system? Would you be able to maintain alk and ca levels by just using Kalk?

 

[Midasblenny]

When you say assists does it actually add buffer or assist by neutralising acid in the system? Would you be able to maintain alk and ca levels by just using Kalk?

No, it doesn`t add buffer but the OH ion will contribute to `building` carbonate which is what we are measuring `kH`is carbonate hardness. Neither does it neutralize acid but obviously due to the caustic nature of CaOH it will increase pH.
I doubt whether any system even those with very few or no calcium demanding corals will be able to have stable calcium levels by using kalk alone, there just isn`t enough calcium available in a kalk solution. Definetly not with its buffering effect, also weak and a mixture of carbonates, bicarbonates and borates are needed for effective or rather balanced alkalinity.

 

[palmerc]

Hydroxide can be converted to carbonate in the system, to provide buffering capacity, but I'm not sure how efficient it's conversion to alkalinity is. i dont think as quick as RHF leads us to believe in the extract from his article below

(We used to manufacture alkaline cleaners (hydroxide-based) which became ineffective after a while (period of weeks) due to it's conversion to carbonates which are not as effective for cleaning. This was especially true in spray systems where the cleaner had more reaction with carbon dioxide)


Also a lot of alkalinity is lost due to other processes so a one to one addition ratio of calcium and alkalinity (like kalk powder) will still require addition of a decent buffer supplying carbonates, bicarbonates etc.

Extract from here http://reefkeeping.com/issues/2005-01/rhf/index.php

"The calcium ions in the solution obviously supply calcium to the aquarium, and the hydroxide ions supply alkalinity. Hydroxide itself provides alkalinity (both by definition and as measured with an alkalinity test), but corals consume alkalinity as bicarbonate, not hydroxide. Fortunately, when limewater is used in a reef aquarium, it quickly combines with atmospheric and dissolved carbon dioxide and bicarbonate to form bicarbonate and carbonate:

4. OH- + CO2 à HCO3-
5. OH- + HCO3- à CO3-- + H2O
​

In an aquarium with an acceptable pH, there is no concern that the alkalinity provided by limewater is any different from any other carbonate alkalinity supplement. The hydroxide immediately disappears into the bicarbonate/carbonate system. In other words, the amount of hydroxide present in aquarium water is really a function of only pH (regardless of what has been added), and at any pH below 9, it is an insignificant factor in alkalinity tests (much less than 0.1 meq/L). Consequently, the fact that alkalinity is initially supplied as hydroxide is not to be viewed as problematic, except as it impacts pH (see below)."