Why is my calcium so high?

[tableforglasses]

Looking for some help figuring out why my calcium is so high.

My 300-gallon reef (about 365 gallons total volume) has been consistently testing around 650 ppm calcium, and I’m not dosing any calcium, 2-part, kalk, or anything else.

Here are the details:

• Salinity: 35 ppt
• Alk: 9.28 dKH
• Calcium: ~650 ppm
• Magnesium: 1279 ppm
• Nitrate: 1.0 ppm
• Phosphate: 0.20 ppm
• Salt: Regular Instant Ocean — NOT Reef Crystals
• RO/DI water tests at 0 calcium
• Freshly mixed Instant Ocean at 35 ppt tests around 650 ppm calcium
• Display also tests around 650 ppm
• Calcium has been verified with both my Neptune Trident and a Salifert test kit
• With the Salifert test, I use the entire first syringe of Ca-3 and about another 0.10 mL before reaching the endpoint
• I’ve gotten similar high calcium readings from multiple bags of Instant Ocean
• I do roughly 20% weekly water changes

The tank is about 7 years old. I actually switched to regular Instant Ocean specifically because I was trying to bring the calcium down, but it hasn't moved much.
I have tested freshly mixed saltwater multiple times and it's also around 650, and I have tested unmixed RODI from my system and calcium is 0. I'm confused about where the calcium is coming from.

Has anyone experienced regular Instant Ocean mixing anywhere near this high at 35 ppt? Is there something about my mixing process or testing that I'm overlooking?

Any ideas on what I should check next?
Thanks for the help!

 

[Decamicron Labs Verified Sponsor]

Have you tried with a different batch or brand?

 

[Piotrek]

You alk is also high. Are you sure you are mixing and measuring correctly? Maybe you have an issue e.g with salinity meter and actually mix too much salt?

 

[Randy Holmes-Farley Verified Community Expert]

Test error is certainly likely. Try the test on new salt water.

 

[tableforglasses]

yeah i am running the test both on the tank and on the new water. I have a redundancy with the salifert test and my trident getting similiar readings, so i don't think it's a test error. I also have redundancy on the salinity as i have a neptune salinity probe (which i know can be inaccurate) and a refractometer that i calibrate weekly and it is reading correctly. I had the same issue when I was running HW marinemix which is why i switched to instant ocean, because i was trying to lower the calcium. I know it makes no sense, that's why I am here, i just can't figure it out.

 

[KQuillan]

You alk is also high. Are you sure you are mixing and measuring correctly? Maybe you have an issue e.g with salinity meter and actually mix too much salt?

My ALK runs high, over 11.

 

[mcarroll]

The tank is about 7 years old. I actually switched to regular Instant Ocean specifically because I was trying to bring the calcium down, but it hasn't moved much.

The chances of ALL THE TEST KITS being "off" but "together" along with all the salt mixes being "off" but "together" is practically infinitesimal.

This tells me you are missing something that's going on.

If you test the same sample of new saltwater three times in a row (pick your favorite test), do all three of your test results match each other pretty closely? (Secondarily, do they match expected results for the salt mix?)

 

[Randy Holmes-Farley Verified Community Expert]

Looking for some help figuring out why my calcium is so high.

My 300-gallon reef (about 365 gallons total volume) has been consistently testing around 650 ppm calcium, and I’m not dosing any calcium, 2-part, kalk, or anything else.

Here are the details:

• Salinity: 35 ppt
• Alk: 9.28 dKH
• Calcium: ~650 ppm
• Magnesium: 1279 ppm
• Nitrate: 1.0 ppm
• Phosphate: 0.20 ppm
• Salt: Regular Instant Ocean — NOT Reef Crystals
• RO/DI water tests at 0 calcium
• Freshly mixed Instant Ocean at 35 ppt tests around 650 ppm calcium
• Display also tests around 650 ppm
• Calcium has been verified with both my Neptune Trident and a Salifert test kit
• With the Salifert test, I use the entire first syringe of Ca-3 and about another 0.10 mL before reaching the endpoint
• I’ve gotten similar high calcium readings from multiple bags of Instant Ocean
• I do roughly 20% weekly water changes

The tank is about 7 years old. I actually switched to regular Instant Ocean specifically because I was trying to bring the calcium down, but it hasn't moved much.
I have tested freshly mixed saltwater multiple times and it's also around 650, and I have tested unmixed RODI from my system and calcium is 0. I'm confused about where the calcium is coming from.

Has anyone experienced regular Instant Ocean mixing anywhere near this high at 35 ppt? Is there something about my mixing process or testing that I'm overlooking?

Any ideas on what I should check next?
Thanks for the help!

Is your ro/di a low ppm tds? Many calcium kits cannot read 10 ppm, but that calcium amount would keep on accumulating.

 

[Randy Holmes-Farley Verified Community Expert]

I still say it is most likely test error if fresh IO and a tank that must have used multiple buckets of salt both read 650 ppm.

Are you sure you are not reading the Salifert kit backwards? Folks often do that.