Kalk and brs 2 part, alk usage way up but ca same

[Reef Altitude]

I have seen many threads about 2 part precipitation, but not sure how kalk would impact this. I have a stirrer doing 1.5 gallons per day (230 gallon system) andtwo part is75 ml of alk/ca. Alk was 7.8 and ca is 410. I increased alk (soda ash) to try to drive it up over 8 but it's just not really increasing. Did not change ca. Mag (mag chloride, my sulfate was getting really high with kalk and mg sulfate) is 1370. I am not seeing a coat of precipitate on anything and the sand is not fusing into concrete or anything. Ph is 7.9-8.1 through the day.

So is this likely precipitation making it not increase or could my demand be uneven or something else?

The steps in many other threads the recommended action (stop dosing and gradually bring it back up)? Does the kalk change anything?

 

[MnFish1]

I would double check your tests to be certain they are correct. It is possible that some of your Ca is precipitating, however, how much coral do you have? do you have any other organisms that use alkalinity/Ca (i.e. large clams) etc? How much did you increase your 2 Part, and how long after you changed your dosing did you check it? Usually with precipitation, you will see it somewhere - and you describe looking at all the right places - but it can still be occurring. Are you dosing your 2 part at different times of the day? or far apart from each other?

 

[Reef Altitude]

I have a reef dose going hourly, with 10 minutes between alk and ca. Plenty of stoney coral so not surprised about demand, it's the uneven demand that seems weird, along with dosing a alk adjustment dose manually into the overflow not increasing anything (30 ml should increase .3 dkh per the calculator. I set the pump from 65 ml per day up to 105 per day over a couple of weeks.
Only increased ca from 65 to 75ml.

 

[Reef Altitude]

Forgot to mention the dosing lines dump into the sump in the skimmer outlet turbulence and the soda ash barely looks milky it mixes so fast. Not seeing dusty powdery stuff either when it dispenses.

 

[Randy Holmes-Farley]

Higher pH accelerates precipitation, so kalk will accelerate it.

It consumes 2.8 dKH of alk for each 18-20 ppm of calcium. No uneven consumption can be due to precipitation.

 

[MnFish1]

I have a reef dose going hourly, with 10 minutes between alk and ca. Plenty of stoney coral so not surprised about demand, it's the uneven demand that seems weird, along with dosing a alk adjustment dose manually into the overflow not increasing anything (30 ml should increase .3 dkh per the calculator. I set the pump from 65 ml per day up to 105 per day over a couple of weeks.
Only increased ca from 65 to 75ml.

just going to say - very nice tank. The rest I think has been said

 

[Reef Altitude]

Higher pH accelerates precipitation, so kalk will accelerate it.

It consumes 2.8 dKH of alk for each 18-20 ppm of calcium. No uneven consumption can be due to precipitation.

So basically, something is consuming the alk because if it was precipitation both ca and alk would be dropping out together, my ca "demand" would also be rising. Because it's not something else is happening?

Thanks for the help, it's good to understand why instead of just changing things hoping it helps.

 

[Randy Holmes-Farley]

So basically, something is consuming the alk because if it was precipitation both ca and alk would be dropping out together, my ca "demand" would also be rising. Because it's not something else is happening?

Thanks for the help, it's good to understand why instead of just changing things hoping it helps.

My guess is that you just cannot detect the calcium change well since alk only mechanisms, such as accumulating nitrate, act slowly.

 

[MnFish1]

@Randy Holmes-Farley - is there a stoichiometric relationship between the amount of Mg++ and the amount of precipitation and pH. I.e. can you mitigate precipitation in tanks with a high pH with a higher Mg level - and is there a 'formula'? Thanks

 

[Reef Altitude]

I am driving my mg up past 1400. It was around 1370 before.

Most threads indicate higher mg reduces precipitation so going that solves it.

I did also add about 10 lbs of crushed coral in bags as bio media to the sump to try to harbor benign bacteria, some cyano was creeping around in the display. Not sure if that's a possible impact or not but it was a similar time to when the alk consumption went way up.

Is this fresh crushed coral creating precipitate sites?

 

[Randy Holmes-Farley]

Magnesium does reduce precipitation tendency, but the degree of effect may be overstated by many. Phosphate and organics also play a big role, maybe bigger than magnesium. Bacteria as well.

 

[Randy Holmes-Farley]

@Randy Holmes-Farley - is there a stoichiometric relationship between the amount of Mg++ and the amount of precipitation and pH. I.e. can you mitigate precipitation in tanks with a high pH with a higher Mg level - and is there a 'formula'? Thanks

No. There is no formula.