pH impact on Alkalinity and Calcium?

[Zitadel]

Hello,

I have thriving 220g sps tank. Two months ago I installed pH probe and started monitoring the swings during day and night. My pH values on that time were between 7.9 at night and 8.1 at day. That time I dosed 165 ml of balling solutions of each container.

I decided to increase the pH with co2 scrubber to see how my corals would react. The impact on pH was fast and now my pH is 8.3 night and evening before lights go out it´s 8.47. Corals have responded very well with better polyp extension and growth speed. I knew my dosing consumption would go up to maintain KH in 8.5 and CA in 430 values. But I did not expect that I would need to dose 320 ml of each container during 24h to keep them in level.

My question is: Would it be easier (lower dosing quantities) to keep my KH and Ca in level with pH around 8.45 if I would settle for lower KH and Ca values?

I assume that I increased the abiotic precipitation and consumption by corals by increasing pH. But would be nice to keep the pH in this range with slightly lower balling solution consumption.

M

 

[Tripod1404]

My advise, dont chase pH.

 

[homer1475]

For a tank that size, and daily consumption, I would be looking into a calcium reactor. While a CA reactor isn't cheap to get setup, when you get to dosing levels that high, reactors become cheaper in the long run.

 

[bertoni]

I don't know how much abiotic precipitation might be occurring. Lowering the alkalinity level might help some, as might lowering the calcium level. If abiotic precipitation actually is causing a lot of the fall, dosing a low pH (baking soda) formula might help. I'm not sure what brand or recipe you're using, but I'd give baking soda a shot.

I think that a calcium reactor is a fine idea to try if you are interested.

 

[Zitadel]

So just to clarify. I do not have issue with the current system. I am happy with the balling dosing and I am not chasing pH. This is more like a test to see what happens if I maintain higher pH. Now it seems that this higher pH has some positive effects on the growth.

I will continue to keep my pH high. Still my question remains that does anyone know how the higher pH lower my KH and Ca and does the lowering effect decrease if I bring the levels closer to natural sea values?

 

[bertoni]

The higher pH encourages more growth from the corals, as you've seen, which can increase supplement consumption dramatically. It also will tend to increase abiotic precipitation, although that's usually (but not always) negligible.

 

[hkgar]

My daily consumption of dKH is about 3.5. I use a Ca reactor as the dosing would be 362 of part 2

Tank is a 180.

 

[reefgeezer]

I'm not a chemist but I stayed in a Holiday Inn a few weeks ago. :hmm5: I think you have reduced the excess dissolved CO2 level that was depressing the pH in your system. You are seeing better growth and increased consumption because of that... less CO2 to free hydroxyls (sp?)... more O2. All good!

If I understand the process correctly, you aren't changing the chemistry of the carbonate/bicarbonate system when removing excess CO2, just the measured pH. You could find that lowering alkalinity by 1 dKh or so will have only a minor effect on pH. Lowering calcium won't have much effect as long as there is enough to meet the system's needs. Coral growth shouldn't be affected once stability returns, but personally, I'd leave well enough alone.

Have you read Randy's Article: "https://www.advancedaquarist.com/2002/5/chemistry"]https://www.advancedaquarist.com/2002/5/chemistry

 

[Zitadel]

Yes in higher pH environment the coral has easier time of getting rid of excessive hydrogen that is increasing the acidity inside the coral. So when pH is high there is less hydrogen atoms in water. If I have understood correctly the bicarbonate form is increasing the hydrogen in water.

But the main question that I was after: Can I decrease the amount of dosing if I keep lower KH and Ca values still keeping the pH in high side? I am starting to think that the answer to this is no. As long as the pH stays high there is higher consumption due to coral + other organisms ability to utilize more and also if there is some precipitation.

I am no chemist so if someone knows better that would be awesome to know. But in any case am thankful of your replies

 

[reefgeezer]

Yes in higher pH environment the coral has easier time of getting rid of excessive hydrogen that is increasing the acidity inside the coral. So when pH is high there is less hydrogen atoms in water. If I have understood correctly the bicarbonate form is increasing the hydrogen in water.

But the main question that I was after: Can I decrease the amount of dosing if I keep lower KH and Ca values still keeping the pH in high side? I am starting to think that the answer to this is no. As long as the pH stays high there is higher consumption due to coral + other organisms ability to utilize more and also if there is some precipitation.

I am no chemist so if someone knows better that would be awesome to know. But in any case am thankful of your replies

In the end, pH is a measure of the results of the interaction of alkalinity & CO2. If alkalinity changes and everything else stays the same, pH will change proportionally. If CO2 changes, and everything else remains the same, pH changes inversely.

So if you don't dose as much of whatever you use to maintain alkalinity kH will fall & so will pH. It won't drop much if you lower your kH from 8.5 to 7... but it will drop. The theoretical pH difference between 7 & 8.5 dkh is about .1 as the curve is pretty vertical above a dKh of 7. SO the answer to your question is "knd of"... You should be able to reduce dosing and allow your kH to fall to NSW levels and pH will stay pretty high... but it will drop a little.

Post industrial CO2 levels are depressing pH and it is said to be getting worse. Well sealed houses concentrate CO2 also. Stripping CO2 is expensive. If I could get 8.0/8.2 during the day and 7.8/8.0 at night I'd be happy and not screw with it. Additionally, 8.5 dKh is pretty easy to maintain and keep stable. FWIW, that's where I keep mine now. I have no idea what the pH in my system is though.

 

[bertoni]

But the main question that I was after: Can I decrease the amount of dosing if I keep lower KH and Ca values still keeping the pH in high side?

Reducing the alkalinity a bit might reduce coral growth some. I am not sure that I'd expect a significant difference if the alkalinity is kept at 7 dKH or higher, though. The same logic applies to calcium at 350 ppm. You could try it, given how easy it'd be.

 

[bertoni]

Yes in higher pH environment the coral has easier time of getting rid of excessive hydrogen that is increasing the acidity inside the coral. So when pH is high there is less hydrogen atoms in water. If I have understood correctly the bicarbonate form is increasing the hydrogen in water.

As the pH increases, the ratio of carbonate to bicarbonate gets larger. Carbon dioxide forms carbonic acid when it dissolves, which releases an H⁺ ion, which will then in many cases bind to a carbonate ion, producing bicarbonate. It's actually an equilibrium situation, with bonds continually breaking and reforming.