Alkalinity Issue

[Merv49]

Is it normal for alkalinity levels to decrease while calcium stays high? I keep testing and find that my calcium levels remain pretty constant at the 470 - 530 levels while my alkalinity seems to go low normally. Usually 8.5 a couple days after I raise it with Soda ash to 9.5. I have kalkwasser but don't want to raise my calcium any higher so I just use the soda ash for alkalinity. Is this normal?

My tank is 200 gal with 37 coral frags and 17 fish so far. All my other water peramaters seem fine with 0 nitrates, phos at .02, mag at 1470.

 

[A13X]

Is 8.5 the lowest it comes down to?
8.5 is still within a good range in my opinion

 

[Merv49]

Yes, so far. Just wondering if it’s normal for one value to go lower and how it relates to dosing with kalkwasser. I was using kalk in my ATO but calcium was in high 500 range so I resorted to just using the soda ash

 

[coil1002]

I keep my Alk at 8.5 and my calcium at 450. I lose about .1 dkh a day if I don't dose, and my calcium will often not dip more than 50 in a week. I have mostly montipora in my tank and they are Alk hogs from what I am seeing. I think 8.5 is a good number to keep your Alk at. I dont use Kalk because I use more alk than calcium. That's why I like 2 part I can dose my Alk and not worry about driving up my calcium.

So to sum it up yes I do think its normal to use more Alk than calcium there is less of it in the water. Corals use both the to build skeletons.

 

[yort265]

Is it normal for alkalinity levels to decrease while calcium stays high? I keep testing and find that my calcium levels remain pretty constant at the 470 - 530 levels while my alkalinity seems to go low normally. Usually 8.5 a couple days after I raise it with Soda ash to 9.5. I have kalkwasser but don't want to raise my calcium any higher so I just use the soda ash for alkalinity. Is this normal?

My tank is 200 gal with 37 coral frags and 17 fish so far. All my other water peramaters seem fine with 0 nitrates, phos at .02, mag at 1470.

I just saw a video of a guy that had the exact same problem as you. Alk would drop, but Cal remained pretty constant. After some troubleshooting and a couple of weeks of very regular testing, he found that the Mag was being used in place of the Cal. When he lowered his Mag from 1450-1500 down to ~1300, his Cal began to drop normally. May be something to try, idk?

 

[Merv49]

I just saw a video of a guy that had the exact same problem as you. Alk would drop, but Cal remained pretty constant. After some troubleshooting and a couple of weeks of very regular testing, he found that the Mag was being used in place of the Cal. When he lowered his Mag from 1450-1500 down to ~1300, his Cal began to drop normally. May be something to try, idk?

Thanks for the suggestion. My mag has been a little high. I will see how it works out.

 

[jsker]

How old is the system? and it could be the salt mix that you are using that is keeping the Ca and Mg high. The Kalkwasser is going to keep the Ca high also. I stopped running kalkwasser in my ATO and switch to dosing.

 

[Merv49]

How old is the system? and it could be the salt mix that you are using that is keeping the Ca and Mg high. The Kalkwasser is going to keep the Ca high also. I stopped running kalkwasser in my ATO and switch to dosing.

My system is 4 months old. I did a Triton test which directed me to add mag. Prior to that I was using kalkwasser. I’ve stopped adding kalkwasser for the time being and just control my all with soda ash, but as you suggest I may switch to two part to better control my calcium and alkalinity going forward.
Thanks

 

[jsker]

My system is 4 months old. I did a Triton test which directed me to add mag. Prior to that I was using kalkwasser. I’ve stopped adding kalkwasser for the time being and just control my all with soda ash, but as you suggest I may switch to two part to better control my calcium and alkalinity going forward.
Thanks

Your Welcome, one thing to take in consideration is that you system is a newer system and the swing are expected as the system adjusts. Mine did this up until I started dosing

 

[Randy Holmes-Farley Verified Community Expert]

I just saw a video of a guy that had the exact same problem as you. Alk would drop, but Cal remained pretty constant. After some troubleshooting and a couple of weeks of very regular testing, he found that the Mag was being used in place of the Cal. When he lowered his Mag from 1450-1500 down to ~1300, his Cal began to drop normally. May be something to try, idk?

If he concluded that, he was definitely wrong.

 

[Randy Holmes-Farley Verified Community Expert]

Is it normal for alkalinity levels to decrease while calcium stays high? I keep testing and find that my calcium levels remain pretty constant at the 470 - 530 levels while my alkalinity seems to go low normally. Usually 8.5 a couple days after I raise it with Soda ash to 9.5. I have kalkwasser but don't want to raise my calcium any higher so I just use the soda ash for alkalinity. Is this normal?

My tank is 200 gal with 37 coral frags and 17 fish so far. All my other water peramaters seem fine with 0 nitrates, phos at .02, mag at 1470.

If both calcium and alkalinity start high (say, 550 ppm calcium and 12 dKH), and you let normal processes proceed to precipitate calcium carbonate (coral skeletons, coralline algae, abiotic precipitation, etc.), you will lose 1 meq/L (2.8 dKH) of alkalinity for each 18-20 ppm of calcium.

So after some consumption, the alk could drop to 7 dKH (a drop of 5 dKH) while calcium is still 516 ppm or so.

Thus it "appears" that alkalinity dropped a lot and calcium didn't, but it is just the math of seawater and calcium carbonate.