Calcium and Alkalinity

[jayman19]

Hello all,

so the past few days I’ve been tracking my alkalinity and calcium consumption. I’ve seen that my tank 55 gallons used about 10ppm calcium in 24 hours, and my alkalinity drops about 0.3-0.5 dKh in 24 hours. Currently I dose Red Sea Calcium and Sodium bicarbonate for alkalinity. I’m wondering how I would use kalkwasser instead to maintain calcium at around 430 and ~8 alkalinity. I don’t want to throw everything out of whack or see a massive jump in alkalinity to keep calcium stable using kalkwasser. Any advice? Please let me know if you have any questions that could help!

 

[arking_mark]

Generally speaking. Our Ca measurement kits aren't accurate enough to really track Ca accurately. Think +/- 10%.

Rule of thumb is to use Alk consumption for dosing both alk and Ca...and trace ion/elements.

There are additives that would impact alk such as dosing nitrate. So a more complete picture of your tank supplementation may be useful.

Those that use balanced dosing like Kalkwasser often have to lower Ca a little after long term use.

 

[jayman19]

Generally speaking. Our Ca measurement kits aren't accurate enough to really track Ca accurately. Think +/- 10%.

Rule of thumb is to use Alk consumption for dosing both alk and Ca...and trace ion/elements.

There are additives that would impact alk such as dosing nitrate. So a more complete picture of your tank supplementation may be useful.

Those that use balanced dosing like Kalkwasser often have to lower Ca a little after long term use.

The only things I dose are calcium, alkalinity, and magnesium when needed. My nitrates are steadily beneath 5ppm and phosphates I don’t do anything for as well.

So it’s better to maintain Alkalinity using kalkwasser and let calcium sort itself out?

 

[arking_mark]

The only things I dose are calcium, alkalinity, and magnesium when needed. My nitrates are steadily beneath 5ppm and phosphates I don’t do anything for as well.

So it’s better to maintain Alkalinity using kalkwasser and let calcium sort itself out?

Again, generally speaking, as long as Ca is abundant it's not something I worry about. If it gets too high you can have a precipitation event. So for my tank I target above 400 and below 500.

Tank Ca/Alk consumption is somewhere around balanced with Ca being slightly lower as phosphate and other other elements will substitute Ca in calcium carbonate. Every tank is different.

The "problem" with measuring Ca is our test kits. Let's say your actual Ca is 500ppm. With +/- %10 you could read as high as 550 or as low as 450. So using those measurements to adjust or dose is risky.

For my tank, I just use balanced dosing. Over 9 months or so my Ca will eventually get to 500+ (from around 450). I use quarterly ICP tests to assess my Ca levels. They are more accurate than my measurements. Then for a week or two I stop balanced dosing and just dose Alk...which for my tank will drop the Ca by about 50ppm.

 

[Randy Holmes-Farley Verified Community Expert]

Hello all,

so the past few days I’ve been tracking my alkalinity and calcium consumption. I’ve seen that my tank 55 gallons used about 10ppm calcium in 24 hours, and my alkalinity drops about 0.3-0.5 dKh in 24 hours. Currently I dose Red Sea Calcium and Sodium bicarbonate for alkalinity. I’m wondering how I would use kalkwasser instead to maintain calcium at around 430 and ~8 alkalinity. I don’t want to throw everything out of whack or see a massive jump in alkalinity to keep calcium stable using kalkwasser. Any advice? Please let me know if you have any questions that could help!

Use kalkwasser to maintain alk, then watch long term (weeks or longer, not days) and see what is happening to calcium and if any changes or additional dosing is needed.

Use this calculator to see how much saturated limewater (kalkwasser) is needed for that alk demand:

Reef Chemistry Calculator