HELP: Alkalinity is high

[Y0U]

Hello, new to reefing and I decided to test water today.

Right now I only have test kits for
Salinity 1.025 (refractometer)
pH 8.0 (salifert)
Alkalinity 20.0 (Hannah)
Calcium 562 (Hannah)
Magnesium 1390 (Hannah)

I buy my water salt and RO/DI from my lfs. I think this last batch of saltwater I bought the guy said it was instant ocean.

Fish and inverts seem fine, cleaner shrimp is acting slightly more shy.

I’m going to do a water change today when I get home from church.

Any advice would be appreciated.
Thank you

 

[Randy Holmes-Farley Verified Community Expert]

If you have not added alkalinity, and are not using artificial rocks, the alk is almost certainly from the lfs water.

Do you have any of that water still to test?

How old is the tank? What is in it?

 

[Peer.Boerner]

Any chance you tested right after adding the water? I ask because if your base rock was not rinsed and soaked in some RO water afterwards the resulting dust from the rock (likely calcium carbonate) will react with the sea water and result in a short term false reading. Curious about the result in a day or so. While Instant Ocean may not be considered a premium salt, many, many people, myself included, have used it and gotten good water parameters, so I’m less likely to think it’s the salt. But, who knows?

 

[Randy Holmes-Farley Verified Community Expert]

Any chance you tested right after adding the water? I ask because if your base rock was not rinsed and soaked in some RO water afterwards the resulting dust from the rock (likely calcium carbonate) will react with the sea water and result in a short term false reading. Curious about the result in a day or so. While Instant Ocean may not be considered a premium salt, many, many people, myself included, have used it and gotten good water parameters, so I’m less likely to think it’s the salt. But, who knows?

Just a minor clarification. Calcium carbonate dust will give a false high reading by dissolving into the alk and calcium tests, but it generally won’t just dissolve into just tank water since seawater is already supersaturated with respect to calcium carbonate.

 

[Peer.Boerner]

Any chance you tested right after adding the water? I ask because if your base rock was not rinsed and soaked in some RO water afterwards the resulting dust from the rock (likely calcium carbonate) will react with the sea water and result in a short term false reading. Curious about the result in a day or so. While Instant Ocean may not be considered a premium salt, many, many people, myself included, have used it and gotten good water parameters, so I’m less likely to think it’s the salt. But, who knows?

Just a minor clarification. Calcium carbonate dust will give a false high reading by dissolving into the alk and calcium tests, but it generally won’t just dissolve into just tank water since seawater is already supersaturated with respect to calcium carbonate.

Thanks for that clarification. This actually happened to me when I foolishly put b piece of base rock into my tank right from the LFS (high quality place I trust). I got a very high Alk reading (11.5 dKh) and thought my dosing was way off. Next day back to 7.6. Thought the alk was a spike but your explanation help me understand why the corals didn’t get a shock from the perceived alk spike.

 

[Y0U]

If you have not added alkalinity, and are not using artificial rocks, the alk is almost certainly from the lfs water.

Do you have any of that water still to test?

How old is the tank? What is in it?

I do have some of the salt water form the lfs. I will test that before I do my water change.

I am not dosing anything and I only have live rock and live sand.

 

[Y0U]

Oh and tank is two months old.

Stocked with
5 hermits
3 nassarious
1 red emerald
1 skunk cleaner shrimp
1 horseshoe crab
2 ocellaris clowns
1 banggai cardinal
1 royal gramma
1 anthias

 

[Y0U]

I just tested my salt water from the lfs and alkalinity is 8.4 dKH

 

[Y0U]

Ok, now I just retested alkalinity of the tank and it reads 8.1. I’m not sure which is the correct reading.

Should I still do the water change? I’m guessing that won’t hurt.

 

[Randy Holmes-Farley Verified Community Expert]

I’d assume the high reading was an error of some sort and proceed as normal. :)

 

[Y0U]

Thank you so much. I didn’t mean to sound a false alarm. That was the first time I tested that the parameters were so out of whack.

I just did a 10% water change. It was due. Cleaned the protein skimmer, the heater and filter sock.

 

[Randy Holmes-Farley Verified Community Expert]

No problem.

Happy Reefing!