Kalk Stirrer for pH boosting only

[ReefCowboy]

Have an sps 150 gal that has been doing great. Only issue is pH hovers between 7.7-8.1.

My alk and Ca levels are on point through 2 part dosing.
I got a kalk stirrer and want to drip it through a dosing pump to keep pH between 8.2-8.4.

So here are my questions:

1- the volume of the stirrer is 1 gallon. How many tsp to saturate it? I followed the instructions on the kalk bag of 2 tsp and there is no deposit at the bottom of the reactor body.
I havent dosed any yet.

2- I was planning on dosing according to pH vs evaporation(ATO) in order to be more precise. I have an Apex and planned on slowly ramping pH over the next few days and drip when pH dropped to keep it at target levels. I also planned to set some safeties to avoid excessive drip.
Is my thinking wrong?

[dkeller_nc]

No, it can be done. But it can be complex, since the kalkwasser will add alkalinity to the system. Presuming that you have SPS, the general rule is stability, stability, stability, especially with respect to alkalinity.

Because of this, you'd probably want to set the amount of kalkwasser dosed to your system at some fixed amount below the minimal evaporation rate, and keep your ATO on and functional. That way, you'll be able to adjust your 2-part dosing or calcium reactor effluent to compensate for the alkalinity added by the kalkwasser to keep the overall alkalinity in your system stable.

Unfortunately that means controlling the amount of kalkwasser based on the pH level is not possible, but the additions of kalk will boost it some.

[ReefCowboy]

Originally Posted by dkeller_nc

No, it can be done. But it can be complex, since the kalkwasser will add alkalinity to the system. Presuming that you have SPS, the general rule is stability, stability, stability, especially with respect to alkalinity.

Because of this, you'd probably want to set the amount of kalkwasser dosed to your system at some fixed amount below the minimal evaporation rate, and keep your ATO on and functional. That way, you'll be able to adjust your 2-part dosing or calcium reactor effluent to compensate for the alkalinity added by the kalkwasser to keep the overall alkalinity in your system stable.

Unfortunately that means controlling the amount of kalkwasser based on the pH level is not possible, but the additions of kalk will boost it some.

Thank you. So I assume I will have to lower my 2 part dosing regimen as well to compensate for the Kalk dosing, so alk isnt being raised excessively?

In other words I would have to start with a minimal dose and test alk daily until it is stable?
Man that is a bummer, i was under the impression I could drip it solely based on pH... it is more work than I anticipated for sure

[dkeller_nc]

Yes, you'll have to compensate to keep the alkalinity in your tank stable. One plus for you is that the amount of alkalinity in saturated kalkwasser is fairly low, so you can add quite a bit of it without having to radically cut down on your 2-part.

One strategy to start with this would be to measure your evaporation over several days, then substitute in 2/3rds of that volume with measured dosing of kalkwasser. When you start this, turn off your 2-part dosing, and measure your alkalinity every day. You can then start your 2-part dosing at a much lower rate, continue to measure the alkalinity daily, and "dial it in". Actually doing it is not as complex as writing it out....

[bertoni]

2 tsp per gallon is about saturation. I'd add a bit extra since some of the "lime" probably will be contaminants, and extra lime will dissolve when more fresh water is added.

You likely will need to reduce the 2-part, but it's hard to be sure, since the higher pH might encourage more growth. I'd measure and watch for a while.

[ReefCowboy]

Originally Posted by dkeller_nc

Yes, you'll have to compensate to keep the alkalinity in your tank stable. One plus for you is that the amount of alkalinity in saturated kalkwasser is fairly low, so you can add quite a bit of it without having to radically cut down on your 2-part.

One strategy to start with this would be to measure your evaporation over several days, then substitute in 2/3rds of that volume with measured dosing of kalkwasser. When you start this, turn off your 2-part dosing, and measure your alkalinity every day. You can then start your 2-part dosing at a much lower rate, continue to measure the alkalinity daily, and "dial it in". Actually doing it is not as complex as writing it out....

Thank you. I filled the ATO container, measured its level at 6am. Will measure again at around 11pm tonight. It will give me a rough daily evaporation rate.

Tonight will test Alk and Ca, and will start slowly dripping 2/3 of the evaporated volume in kalk, spread over the same amount of hours with my Apex. Will test Alk and Ca again the next day at night and adjust 2 part dosing accordingly.

My thought is starting a kalk dose based on a smaller 1 day’s evaporation volume will give me lesser variance in Alk and Ca so I can correct dosing before those two params change to much. It will be more work testing everyday but feel its safer. Does this sound like a good plan?

Originally Posted by bertoni

2 tsp per gallon is about saturation. I'd add a bit extra since some of the "lime" probably will be contaminants, and extra lime will dissolve when more fresh water is added.

You likely will need to reduce the 2-part, but it's hard to be sure, since the higher pH might encourage more growth. I'd measure and watch for a while.

Thank you Bertoni,
I noticed looking at some videos and researching stirrers that users usually have at least 1/2” of sludge at the bottom of the reactor body. Im assuming that is result of impurities and intended powder measure to last a predetermined length of time.

I read some of that sludge will not ever disolve being it will lose its potency and eventualy need to be removed through the cleaning of the reactor, maybe once a month.

You recommended adding more to make up for water that is diluting the contents being dosed. How much more should I add? Does it matter or could I keep an eye on the sludge layer at the bottom as reference?

The kalk Im using is BRS’s Pharma grade, is it any better than others as far as present contaminants?
During a 24hr period my pH goes from 7.75 to 8.1
Is it better to dose evenly spread through the day or aim to dose more at times when pH is lowest(I can use for reference the pH graph on the Apex).

Thank you all for all help and sorry for so many questions. Im a seasoned reefer but a complete noob for Kalk. Being the tank is on point, Im trying to take things very slow to hopefully maintain as much stability as I can during this process!

[dkeller_nc]

Don't worry about asking questions, most of us come to the forum to help. In my case, I have a PhD in chemical engineering, so chemistry's sort of my "thing".

Yes, your plan sounds good to me. The reason I suggested going with 2/3rds of the evaporation rate as a maximum is that's likely to change over the seasons and with the weather. Right now, it's the heating season, so the interior of houses tend to be dry, which favors evaporation.

What you don't want to happen is for your kalk additions to exceed the evaporation rate, since that will cause your salinity to go down (which, incidentally, will also cause your alkalinity to go down as well).

From the standpoint of kalkwasser reactor evaporation:

When you add kalk to a stirrer, some of it dissolves into the solution until it reaches saturation. Only about 1/4 of a teaspoon per liter will actually dissolve. The solubility of calcium hydroxide is 1.73 grams per liter at 20 degrees C; the density of CaOH2 is 2.21 grams/cm3 (solid). Since it's a powder, about 60% of the volume of the powder is actually a solid. Therefore, (1.73 g/L)/(2.21 g/cm3) = (0.78 cm3 solid/L)/(0.6 cm3 solid/cm3 powder) = 1.3 cm3 kalk powder per liter. If you then do the conversion between cm3 (same as mL) to teaspoons, you get 0.26 teaspoons per liter.

However, that doesn't mean you want to put a quarter of a teaspoon per liter of reactor volume into the stirrer. Since fresh water will be added continually, and you want to maintain saturation, you need "extra", and that's the source of the recommendation to add about 2 teaspoons per liter of reactor volume.

There's another effect that leads to "sludge" at the bottom of the reactor. The incoming water will be saturated with CO2 at the concentration that's in the air in the fish room. All of that CO2 dissolved in the incoming water will react with the kalk powder on the bottom of the reactor to form insoluble calcium carbonate. Not only that, some of the kalk powder that you bought will have already been converted to calcium carbonate while it was a powder from reaction with atmospheric CO2.

So bottom line, you need well in excess of the saturation amount on the bottom of the reactor to ensure saturation of the output.

As far as when to dose, if your objective is to even out the pH fluctuations, then I would set the kalk to dose overnight. If your objective is raise the overall pH period, regardless of the day/night cycle, then I'd spread the 2/3rds evaporation amount over a 24 hour period.

BTW - you will have to empty the reactor, clean it out, and start with fresh kalk powder about once every 2 weeks. Perhaps more often if you're putting a large amount of top-off water through it compared to the reactor's volume.

[ReefCowboy]

Originally Posted by dkeller_nc

Don't worry about asking questions, most of us come to the forum to help. In my case, I have a PhD in chemical engineering, so chemistry's sort of my "thing".

Yes, your plan sounds good to me. The reason I suggested going with 2/3rds of the evaporation rate as a maximum is that's likely to change over the seasons and with the weather. Right now, it's the heating season, so the interior of houses tend to be dry, which favors evaporation.

What you don't want to happen is for your kalk additions to exceed the evaporation rate, since that will cause your salinity to go down (which, incidentally, will also cause your alkalinity to go down as well).

From the standpoint of kalkwasser reactor evaporation:

When you add kalk to a stirrer, some of it dissolves into the solution until it reaches saturation. Only about 1/4 of a teaspoon per liter will actually dissolve. The solubility of calcium hydroxide is 1.73 grams per liter at 20 degrees C; the density of CaOH2 is 2.21 grams/cm3 (solid). Since it's a powder, about 60% of the volume of the powder is actually a solid. Therefore, (1.73 g/L)/(2.21 g/cm3) = (0.78 cm3 solid/L)/(0.6 cm3 solid/cm3 powder) = 1.3 cm3 kalk powder per liter. If you then do the conversion between cm3 (same as mL) to teaspoons, you get 0.26 teaspoons per liter.

However, that doesn't mean you want to put a quarter of a teaspoon per liter of reactor volume into the stirrer. Since fresh water will be added continually, and you want to maintain saturation, you need "extra", and that's the source of the recommendation to add about 2 teaspoons per liter of reactor volume.

There's another effect that leads to "sludge" at the bottom of the reactor. The incoming water will be saturated with CO2 at the concentration that's in the air in the fish room. All of that CO2 dissolved in the incoming water will react with the kalk powder on the bottom of the reactor to form insoluble calcium carbonate. Not only that, some of the kalk powder that you bought will have already been converted to calcium carbonate while it was a powder from reaction with atmospheric CO2.

So bottom line, you need well in excess of the saturation amount on the bottom of the reactor to ensure saturation of the output.

As far as when to dose, if your objective is to even out the pH fluctuations, then I would set the kalk to dose overnight. If your objective is raise the overall pH period, regardless of the day/night cycle, then I'd spread the 2/3rds evaporation amount over a 24 hour period.

BTW - you will have to empty the reactor, clean it out, and start with fresh kalk powder about once every 2 weeks. Perhaps more often if you're putting a large amount of top-off water through it compared to the reactor's volume.

Thank you very much for the elaborate post. That really helped me understand it much better. I will post again once I determine my evaporation rate tonight, and what the recommended powder dosing is from the stirrer manufacturer. I would like to consult such measure here so I can be sure to be on the right path.

Cleaning the reactor every two weeks seems more than I planned, but I’d rather be proactive. For the cleaning, should flushing with RO water be sufficient? I read a vinegar bath every so often is recommended, what are your thoughts?

[dkeller_nc]

The vinegar bath is probably unnecessary. When I was running a kalk reactor, I found that all that was necessary was disconnecting it, rinsing it out (do not pour the sludge down the sink drain!), adding a fresh charge of kalk, and reconnecting it to my system.

Keep in mind that it may not actually be necessary to rinse it out every 2 weeks. More kalk powder can and should be added every few days to a week or so to ensure that you've actually got dissolvable calcium hydroxide in the reactor (instead of calcium carbonate), but the disconnect it, empty it out, and start fresh is largely a consideration of mechanics - making sure that you don't build up so much sludge that it interferes with the stirrer or sharply reduces the reactor volume.

[ReefCowboy]

So I roughly calculated 3.2 liters as the evaporation volume for the day. 2/3’s of that amount is 2.13 liters, so 2,130 mls of kalk dosed spread throughout the day? When my algae scrubber lights go off at 8am my pH starts dropping, usually from 8.0 to 7.7 at 2pm, when my blue leds go on and pH starts climbing up again.

[dkeller_nc]

I would think you'd need to spread the 2.1 liters throughout the 24 hour period. Otherwise, you may see your specific gravity go through cycles as 2/3rds of a day's evaporation is put into the tank in a much shorter time period than 24 hours.

[ReefCowboy]

Got it.
To be honest I was a bit concerned dosing all that from the start, so I'm dosing 1000 mls today and will test alk, Ca/observe the pH... then I'll bump up 300 mls each day until I get to the 2/3 of the total.

[dkeller_nc]

I think several of use would be interested in your results, especially if you can post a pH trace before/after starting the kalkwasser dosing.

[bertoni]

I agree that a pH comparison would be interesting.

[ReefCowboy]

Originally Posted by dkeller_nc

I think several of use would be interested in your results, especially if you can post a pH trace before/after starting the kalkwasser dosing.

Definitely will post graphs and detail everything.
So yesterday at night I noticed dosing 1,000 mls didnt affect pH at all. The values throughout the day were very similar to the usual ones without the kalk stirrer.

I tested Alk and it was stable at the usual 8.6dkh, so I figured would jump the dose to 2,000 mls. I started the larger dose at the evening and the pH has stayed stable at 8.
Im yet to verify it wont dip past 8:00am when my algae scrubber light goes off, which is when it drops below 8.

If I can manage to keep it at 8 until my lights go back on at 2pm it will be progress. I will test Alk tonight and make sure values are stable.
If they are, I might add a bit more the following day until I get pH values in the 8.2 range.

Soon should be able to post the graphs.