Alkalinity spiking

[Hellic]

Over the past several weeks my alkalinity has been spiking. I did switch from reef crystals to regular instant ocean. Maybe 3 or 4 water changes at 20% over the past 2 months. A fresh batch generally tests around 9 or 10 dkh but my alkalinity has shot up to 12dkh for no apparent reason. My doser has not been running as I've turned it off 2 months ago due to the higher readings. Only other thing I've been adding is IO Nitrate Reducer. About 7ml per week in a 50 gallon total volume system.

Dkh 11.8 hanna and (api shows ~11.5dkh)
Calcium 468ppm hanna
Magnesium ~1500ppm salifert
Salinity 35ppt
Softy/LPS tank

My worry is that alkalinity is going to elevate too high since it has been continuously elevating more and more over time. I'm at a loss for what to do since water changes don't seem to be helping.

 

[Pistondog]

Verify your kh test with a 2nd type. I use hanna, but sometimes get squirrelly readings. I verify with red sea alk test.
Test each batch of fresh water until you find the cause.
If your nutrient levels arent too bad, you could wait longer between water changes to allow the alk to be used up and lower on its own.

 

[Rmckoy]

Have you tested to confirm nitrates have been stable ?
A increase in nitrates will cause alkalinity to go up .
actually .. I’ll wait for @Randy Holmes-Farley but I believe either increase or decrease in nitrates will effect alkalinity

 

[Hellic]

Verify your kh test with a 2nd type. I use hanna, but sometimes get squirrelly readings. I verify with red sea alk test.
Test each batch of fresh water until you find the cause.
If your nutrient levels arent too bad, you could wait longer between water changes to allow the alk to be used up and lower on its own.

I guess I wont know for certain until I get a new bottle of reagent. I did check with API kH test and it seems to be a close resemblance to the hanna checker. Nitrates are 10.8

 

[Hellic]

Have you tested to confirm nitrates have been stable ?
A increase in nitrates will cause alkalinity to go up .
actually .. I’ll wait for @Randy Holmes-Farley but I believe either increase or decrease in nitrates will effect alkalinity

They have been relatively stable around 10-11ppm on the hanna checker.