What is this black blob on my fish?

Thresa

AC Members
Sep 15, 2004
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My Royal Gramma was in quarantine for 10 days, when she developed a case of fin rot on her tail. I tried several medications before I found one that worked, which was Furan 2. I gradually dropped the salinity in her tank from 1.022 to 1.018, and I followed the proceedures for treating the fish, and even gave her an extra treatment since her case was so severe (which was part of the instructions). After her treatment was over I did a 25% water change and added activated carbon to the filter (part of the instruction for using Furan 2). The next day her tail fin was getting worse again and she had developed an area black on her side. It does NOT look like little dots, but rather a large blob or area. I added melafix to her tank to for the fin rot and have no idea what to do from here.

1. Do I treat the black blob?

2. Should I start using furan 2 again, or have the bacteria built up a resistance to it?

Thanks for your help,
Thresa
 
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