Cardinal Tetras With Fin Rot

[steve26-2008]

I lossed a cardinal yesterday, so I checked the other fish and could see a little white spot. I dosed the tank with white spot treatment, but woke up today they have in fact got fin rot. Do I need to do the large water change to remove the old treatment first but before adding finrot meds.

 

[KittyKat]

Yes: large water change (90% with warm dechlorinated water, assuming your tap water starts are the same as tank) and if you have some carbon, you can add that to the filter for a day to remove and remaining medication, the remainder should be gone in a day then. After, remove the carbon and start the fin-rot treatment.

If you don't have carbon, a 90% water change today and a 90% water change again tomorrow should do the job.