Can a lower Alk water change cause flashing?

[cshouston]

I did a 20% water change yesterday with TM Pro Reef that I forgot to buffer ahead of time. My tank’s alkalinity dropped from 7.9 yesterday to 7.3 today. It’s normally 8. This morning I noticed two of my fish flashing a little bit, but they were quarantined and have no signs of ich or disease in general. I’m tempted to point the finger at the drop in alkalinity, but wanted to consult others who may have experienced something similar. Can the water change with lower alk water cause flashing in your fish?

 

[Nick Steele]

I’d say it’s very unlikely the cause. I went through a two month period were I was doing water changes weekly with 7.7-8dkh water and tank was at 10-11dkh.

 

[Randy Holmes-Farley Verified Community Expert]

I agree I don't think this can be the cause. I also do not see how a 20% water change could cause this alk drop.

A 20% change with 7 dKH water in an 8 dKH tank would only drop alk to 7.8 dKH.

 

[cshouston]

Perhaps my Hanna checker was off, then. Either way, the flashing stopped and I’ve since corrected the alkalinity. Thanks.

 

[Paul B]

No, that won't affect anything. Mine fluctuates much more than that everyday. Maybe every hour.

 

[cshouston]

No, that won't affect anything. Mine fluctuates much more than that everyday. Maybe every hour.

Thank you! I looked at my tank log and noticed that the pH the day before was 8 because my CO2 scrubber media needed to be replaced. After the water change, and media change, it jumped to nearly 8.4 so I’m beginning to suspect the change in pH may have irritated them. The flashing stopped though, so that’s good!