kalkwasser and high alkalinity

[sghera64]

did u run into pH issues? or did u not really worry about it?

i do notice a lot of people, back east especially, have tanks in their basement and stuff. but i'm in socal and my tank is right next to my front door, which is leave open for many hours a day, along with a lot of other doors. so i was kind of surprised my tank never had high pH naturally, but perhaps i just caught it recently on some bad days and my pH is naturally quite high? idk what the upper range of pH is, seems most want it at 8.4 at most, and i don't really aim to flirt with the absolute top range of anything

Most will shoot to maintain 8.3. Some push 8.5 as the limit. My system is in a basement AND I run a CO2 reactor - - so high pH is definitely not a problem as I max out around 8.2 now (with all the windows open).

You might run into high pH using kalkwasser if your tank is near open windows much of the time. It will depend on when you add the kalk and how much stony coral growth you have. You can mitigate high pH with kalk by limiting your additions to night time. I over add during night and let the system's evaporation catch up during the day. Usually, the ATO (bypassing the kalk reactor) kicks in near the end of the day because I did not add enough kalk over night.

Some folks meter in kalk during the night to match, or partially match, their alk consumption. Allowing straight RO/DI ATO to make up for other evaporation losses. You could do this for the simple reason as to limit the maximum pH.

 

[Dkeller_nc]

Apologies, guys. I've done this calculation a bazillion times, but I can't always remember the amount per gallon vs. the amount per liter.

For saturation, the calculation goes like this: calcium hydroxide saturation at 20 deg C in water: 1.73 g/L (from Wikipedia). Density of solid CaOH2: 2.21 gm/cm^3.

Therefore, (1.73 g/L)/(2.21 gm/cm^3) = 0.783 cm^3/L. That's for solid CaOH2. For any powder, the void volume is about 0.4, so the actual powder volume in a liter at saturation is (0.783 cm^3CaOH2/L)/0.6 = 1.3 cm^3, which is 0.26 teaspoons. So for a gallon, the saturation point is 0.26 * 3.78 = 0.98 teaspoons per gallon.

 

[mattzang]

Apologies, guys. I've done this calculation a bazillion times, but I can't always remember the amount per gallon vs. the amount per liter.

For saturation, the calculation goes like this: calcium hydroxide saturation at 20 deg C in water: 1.73 g/L (from Wikipedia). Density of solid CaOH2: 2.21 gm/cm^3.

Therefore, (1.73 g/L)/(2.21 gm/cm^3) = 0.783 cm^3/L. That's for solid CaOH2. For any powder, the void volume is about 0.4, so the actual powder volume in a liter at saturation is (0.783 cm^3CaOH2/L)/0.6 = 1.3 cm^3, which is 0.26 teaspoons. So for a gallon, the saturation point is 0.26 * 3.78 = 0.98 teaspoons per gallon.

well that's certainly some math that's over my head

so 1 teaspoon is the max you can really do? anymore than that isn't going to actually effect the pH/alk/calcium? i guess i'll give it another go but i'll do like 1 teaspoon per 5 gallons or something to start off with. gonna let my parameters drop a bit first, though.

 

[brewandreef]

Curious, has anybody seen detrimental effects to their reef running at a high pH? Like greater than 8.5?

 

[mattzang]

well i'd say pH of 8.3 definitely sounds pretty awesome. Seems everyone aims for 8.3, 8.4 seems ok, but most people cut it off there via their apex or whatever. i don't have the option to magically turn it off so uh lol

 

[Dkeller_nc]

well that's certainly some math that's over my head

so 1 teaspoon is the max you can really do? anymore than that isn't going to actually effect the pH/alk/calcium? i guess i'll give it another go but i'll do like 1 teaspoon per 5 gallons or something to start off with. gonna let my parameters drop a bit first, though.

The saturation point depends on (among other things) temperature. Unlike most compounds, calcium hydroxide has an inverse saturation amount vs. temperature. If you look at the table about halfway down on the right of the wikipedia page, you'll see that calcium hydroxide's solubility in water is 1.89 g/L at 0 deg C, 1.73 g/L at 20 deg C, and 0.66 g/L at 100 deg C. Some folks add vinegar to their kalk solution, which increases the solubility considerably, though it also means they're carbon dosing.

 

[fish farmer]

When I started using the BRS pharm grade kalk, 1/2 teaspoon per gallon was too hot...I was slow dripping but sometimes would drip too fast and get high alk readings over 10.

I use 1/4 tsp per gallon with a dosing pump out of a container with 3 gallons of kalk. It is on a light timer to turn on 4 times an hour. With this set up, there is no worry of overdosing kalk via an ATO.

 

[mattzang]

The saturation point depends on (among other things) temperature. Unlike most compounds, calcium hydroxide has an inverse saturation amount vs. temperature. If you look at the table about halfway down on the right of the wikipedia page, you'll see that calcium hydroxide's solubility in water is 1.89 g/L at 0 deg C, 1.73 g/L at 20 deg C, and 0.66 g/L at 100 deg C. Some folks add vinegar to their kalk solution, which increases the solubility considerably, though it also means they're carbon dosing.

well i do carbon dose, but not in my ato i just manually add that.

i'm going to test my alk again in a bit and see where it's at. if it has gone down from yesterday i guess i could leave things as is, hopefully adding rodi without kalk yesterday made the topoff water less potent? if it has gone up i'm going to just clean the reservoir out and go with straight rodi for awhile until my alk goes down. i know people do high alk systems, but idk what goes into that, i just want to aim for slightly elevated levels lol

and why do things go poorly in groups in this hobby? my urchin has been full bulldozer lately, knocking 5 frags off of where i glued them in the last 2 days.

 

[mattzang]

and alk is 11.5 today so gonna just clean out the reservoir and go kalkless. *cries* epic kalk fail

 

[Dkeller_nc]

and alk is 11.5 today so gonna just clean out the reservoir and go kalkless. *cries* epic kalk fail

One thing to note is that for those that use kalk on an on-going basis generally use a dosing pump to add it to the tank in an amount that is calculated to be less than the minimum amount of evaporation so that the specific gravity doesn't go down (i.e., they "dose" kalk and use an ATO).

Doing it this way allows one to calculate the amount of kalk necessary to at least partially make up for the alkalinity demand of one's aquarium without actually exceeding it.

 

[Iván Olalla]

and alk is 11.5 today so gonna just clean out the reservoir and go kalkless. *cries* epic kalk fail

Kalk in ATO is very dangerous if you dont crunch your evaporation numbers. On the other hand is cheap and helps boost ph all day long, so keep that in mind. I do use kalk in my pico reef but use a doser instead of the ATO, ph drops to 8.1 at night and in the day it stays around 8.4/8.5

Here´s a calculator i found to be very accurate and that helped me dial my consumption:

https://www.hamzasreef.com/Contents/Calculators/KalkContribution.php

 

[mattzang]

One thing to note is that for those that use kalk on an on-going basis generally use a dosing pump to add it to the tank in an amount that is calculated to be less than the minimum amount of evaporation so that the specific gravity doesn't go down (i.e., they "dose" kalk and use an ATO).

Doing it this way allows one to calculate the amount of kalk necessary to at least partially make up for the alkalinity demand of one's aquarium without actually exceeding it.

yeah i came across that option too, which i'm sure works a lot better to have control, but i was trying to save some money for once with the dang tank and i didn't really want another container of water sitting around. i have a 50 gallon cube and the sump takes up the entire under cabinet area, so my ato is already just sitting next to the tank. i wasn't trying to add another fresh water reservoir sitting around lol.

i guess i just underestimated what my demand was or how potent kalk was or something. seems like you're telling me kalk is pretty weak, but then there's others saying i just put in way too much. but how much i put was over the saturation point so i don't know. or somehow despite me putting my pump several inches above the bottom it was maybe sucking in the undissolved sludge.

i switched my ATO reservoir to a clean one yesterday and i'm just going to go without kalk for awhile. maybe once my levels get back down to where i was trying to keep them i'll give it another go with like 1 tsp per 5 gallons

 

[Iván Olalla]

Curious, has anybody seen detrimental effects to their reef running at a high pH? Like greater than 8.5?

8.1 at night and 8.4/8.5 day...mixed pico reef, no ill effects so far, and i think my acros are growing very well.

I dose kalk every 2 hours via doser and my daily alk consumption is 2.1 dkh

 

[dantimdad]

In my experience you will run a bit higher alk when running kalk.

Mine is 11 and calcium is 435 and I use kalk as top off mixed a tablespoon to 5 gallons of RO water.

 

[BeejReef]

thanks for the in depth response.

so 1/2 teaspoon is the max? is BRS lying?



my understanding was basically, start with 1/2 tsp and go from there. at 2 tsp per gallon, adding more won't do anything, so that's when people that supplement via kalk have to start dosing? but you're saying the max is 1/2 tsp?

also, i have my pump about 3-4" (intake towards the surface) above the bottom of my ATO reservoir. but you're thinking it's sucking in the undissolved stuff still?

so, you'd recommend taking a bucket of RODI and adding the kalk in there, then adding it to my ATO reservoir, but make sure to not add the undissolved stuff at the bottom?

The max is 2tspn/gallon. Beyond that, it just settles out. I use it in my ato reservoir also. Usually easy-peezy.
However, it's not nearly as easy to adjust as two part. If you don't mix in enough, you have to add in and mix in more. Ofc, the mixing makes the original mixture a little less potent than it was, so you're always guessing a little. If you made it too strong, you have to dilute it with RODI (or stir it until it loses potency). Again, not incredibly accurate.

Also, when it gets warm and humid the tank evaporates a lot less, so it throws off your dose. If you're an AC house and you just set a temp for the house and leave it, probably not an issue. We only turn the AC on when it gets "hot" though, so the dosage varies for me. It's to the point now where I'm having a hard time just using kalk to maintain alk/calc. Even though my corals are only frags, the coraline is coming on hard. I expect it to calm down by fall.

You also want your ato output into the sump to be in a pretty high flow area.

 

[dantimdad]

Luckily, my evaporation is pretty consistent - 3 quarts a day.

 

[mattzang]

In my experience you will run a bit higher alk when running kalk.

Mine is 11 and calcium is 435 and I use kalk as top off mixed a tablespoon to 5 gallons of RO water.

hmm that's interesting, but my alk was around 9 and then within a week of starting kalk it was up to 11.5 yesterday. i know some people run higher parameter systems and the BRS experiments on that front yield promising results, but given this is my first reef tank i figured i'd just aim for slightly elevated parameters. something in the alk 9 calcium 450 magnesium 1400 or so range.

i just got greedy always reading/seeing how elevated pH is like steroids for coral growth and who doesn't want more growth?! that was really my hope with kalk was it'd crank up my pH and do some work on the alk/calcium front. i figured i'd still have to dose 2 part to make up for whatever the kalk wasn't, but in a perfect world if it'd just handle the alk/calcium demand of my tank i wouldn't complain. what i didn't forsee was starting at slightly above the 'low demand' range BRS listed and it sending my alk to the moon

 

[dantimdad]

In all honesty, and anyone who knows me, knows I preach this, we chase numbers too much.

I think you should keep an eye on things and see how your corals respond.

If they start looking peaked or in poor health, discontinue kalk or go to a weaker mix and throw in a water change to help level out.

 

[Iván Olalla]

In my experience you will run a bit higher alk when running kalk.

Mine is 11 and calcium is 435 and I use kalk as top off mixed a tablespoon to 5 gallons of RO water.

I keep mine steady at 8.5 (ca 420 mg 1300) dosing 96% kalk saturated solution every 2 hours my dkh consumption is 2.1 daily, around 30 ml every 2 hours

 

[mattzang]

alk down to 10.8 from 11.5 yesterday so maybe in a week or so i'll give 1tsp per 5 gallons a whirl. i shall not be defeated by some cloudy water!