High ph after starting kalk

[jasimek]

I just started kalk the other day after getting parameters in line. Mag 1360, cal 480 and alk 8.8. I have it set up with my ATo water using tunze osmolator. I moved the ph probe to the refugium area and the kalk tops off in the return chamber. The ph has steadily been rising the past few days from about 8.19 to today 8.43. I have my reef keeper elite set to top off only under 8.50. Should the ph be getting this high from kalk? I have a 5 gallon bucket with about 4 gallons rodi water and I used 2 teaspoons per gallon for a total of 8 teaspoons

[animalkingdom]

it depends on your evap. Saturated calcium hydroxide (kalkwasser) has an extremely high pH (12.4) and is very caustic. In theory you could raise your tanks pH pretty close to this pH using kalk if your evap is really high. it sounds like you may need to either decrease your evap or dilute your kalk. if that doesn't keep up with your demand you can always supplement with 2 part or a calcium reactor.
hope that helps

[baldbean]

Tuning in your kalk amount can be tricky. Every time i restart, I do so with just one teaspoon for a 5 gallon water jug. Each week I bump it up by 1/2 a tsp making sure my pH remains in the safe zone (no higher than 8.5).

Like mentioned above, it depends on your evaporation rate. During the summer I use a more watered down mixture (1.5 tsp per 5 gallons), while in the winter I use a less diluted mixture (3 tsp per 5 gallons).

So perhaps you should remove the kalk from your system and wait for your pH to settle down for a couple of days. Then try a mixture of 1 Tsp per gallon, then bump up/down from there.

EDIT:
I use a 5 gallon water jug for my top off controlled by an Apex and administered with a 50 mL/min BRS dosing pump.

[tmz]

Kalk is calcium hydroxide. The oxide makes it basic as it joins with CO2 in the water reducing pH and producing CO3(carbonate alkalinity).
The phH in a tank is dependent on the CO2 in the water. As it depletes from the oxide more CO2 equilibrates from the air around the tank but it takes some time and is dependent on the gas exchange at the surface of the water. Closed tanks and low , surface agitation or aeration can slow this process. Some C02 is also produced by biological activity.

While 8.4 is ok, if you choose, you can slow pH rises associated with calcium hydroxide dosing by :

increasing surface agitation, open water and aeration,

using less than fully saturated limewater(kalkwasser in German),

dosing only clear ;not cloudy, lime water, as the cloudiness likely contains some undissolved calcium hydroxide which will dissolve in the extra dilution of the tank,

spreading out the dose for as long as practicable( 24/7 would be best) but no more than 1/4tsp about 8 grams for 50 gallons of tank water volume in any given hour is reasonably safe in most aquariums. This should allow enough time for CO2 to equilibrate.

adding to the CO2 in the tank. Some do this with calcium reactor use along with kalk.Some by increasing bacteria via organic carbon dosing which produces CO2.

I'd start at less than fully saturated lime water and increase based on demand.Stopping and starting will likely cause alkalinity shifts which can be to some sensitive corals.

[bertoni]

That pH level is safe, so I wouldn't worry that much. More aeration can help limit the pH increase. Does the tank have a skimmer?