lost my first fish in the new tank :(

FishLady - I did start with meds, late Tuesday night. I'm treating with API's anti-parasite med, which has Metronidozole and Praziquantel. I'm also dosing with Melafix.

My female GBR died today, not surprisingly, as she was in really bad shape. My loaches and platy seem better. However, my apisto is failing - he's gasping and bottom sitting.

Does anyone know if there's a way to treat a bacterial infection without wiping out your filter bacteria? They don't sell medicated food in any of the lfs or box stores around here - just the stuff you dose the whole tank with.

Dosing the whole tank with an antibiotic is an absolute last resort for me, as it will mean re-cycling my tank, which, since it's already stocked, will mean a crazy amount of water changes in order to prevent more fish deaths.

And it's definitely disease I'm dealing with - I stopped at the lfs today and picked up a new heater for my QT tank. While I was there, I peeked in at the taeniatus. They're down from around 20 fish, to 4, and nobody has bought any since I did on Friday. Of the remaining four, two look great, nice and vibrant, just like mine were. The other two, while having no visible disease aside from darkening of the head/gills, are bottom sitting and gasping - clearly very ill.
 
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