Why is my alkalinity rising

[Nathd2311]

Could anyone give me a possible explanation as to why my alkalinity could be rising throughout the week when I'm not dosing? This week it's gone from 8.7 to 9.4 I've just done a 10% water change and brought it back down to 9.1. Its only a 20gallon tank.

 

[Randy Holmes-Farley Verified Community Expert]

Could anyone give me a possible explanation as to why my alkalinity could be rising throughout the week when I'm not dosing? This week it's gone from 8.7 to 9.4 I've just done a 10% water change and brought it back down to 9.1. Its only a 20gallon tank.

Not without more info. There are a number of reasons why alk rises, and it may also be test error. That’s not a big change.

Is nitrate falling? Are you dosing it? Are you dosing anything?

Top off water is what?

Calcium carbonate sand slowly dissolves and in a very low alk demand tank, alk can rise.

 

[Nathd2311]

My nitrate has been stable at around 7, my phosphate is low at 0.03 and I use Brightwell neophos to stop it bottoming out. I use rodi to top off. I use tropic marin pro reef salt and alk had been stable at around 7.8ish until couple of weeks ago. The only thing I can think was I had alot of spirobid worms all over the back glass and since scrapping these off alk has starting increasing. Have searched online to see if I could find anything relating to this but with no luck. Thanks for your help

 

[Nathd2311]

My nitrate has been stable at around 7, my phosphate is low at 0.03 and I use Brightwell neophos to stop it bottoming out. I use rodi to top off. I use tropic marin pro reef salt and alk had been stable at around 7.8ish until couple of weeks ago. The only thing I can think was I had alot of spirobid worms all over the back glass and since scrapping these off alk has starting increasing. Have searched online to see if I could find anything relating to this but with no luck. Thanks for your help

I'm pretty sure it's not test error as I'm using hanna alkalinity and testing exactly the same way each time. I tested my fresh salt the same way and that's reading 7.8

 

[Randy Holmes-Farley Verified Community Expert]

it may just be dissolution of sand at the low pH down in it from degradation of organics.

In any case, trying to figure out the way is not always trivial.

If the alk keeps rising you can lower the alk in the new salt water that you use for water changes.

 

[Nathd2311]

it may just be dissolution of sand at the low pH down in it from degradation of organics.

In any case, trying to figure out the way is not always trivial.

If the alk keeps rising you can lower the alk in the new salt water that you use for water changes.

Yeah I think you might be right there would just be nice to put a finger on the cause. Thank you for your time