So I’m new to all of this and I made a mistake. After cycling my 55gallon planted tank, I went to my LFS and bought some Bloodfin (12) and serpae tetras (8)and (6)Cory’s. I spread the purchases out by a few days to help with not spiking ammonia. Well, I didn’t QT them first and put them right in my tank after acclimation. After a few days many of the tetras were sick. Looked like cotton mouth mostly and some hole in the head, no signs of ich I think. I treated the entire tank with API Erythromycin and General cure. The tetras have been dying off so I think I caught it too late. The Cory’s still look very healthy.
What should my next steps be? My cycle is still fine, which is great. I plan to QT all fish from now on but how do I go about making sure my tank isn’t still full of disease to new comers? How do I disinfect without killing off my cycle or plants/snails?
My parameters are this below and I’ve been doing many water changes during meds
Set my water temp to ~80F from my normal which was ~75F