I am really surprised that Furanase didn't wiped out your biofilter after the first dose.
Me too! I have been checking the params daily on the big treatment tank as well as the 10g with the betta being treated, and both bio-filters are 100% working.
When you used Furanase, how long did you use it for and about how many days did it take for fish to look completely cured?
Yesterday I woke up to a dead guppy in there, and it wasn't even one that had any "rot" of any kind. So it was either too much salt to handle or too much medication. I did about 45% PWC, adding new water back slowly over the evening, without any salt or meds added last night. I haven't replaced carbon yet because I plan to continue treatment. There is still medication in the water because it's still tinted brown. Whether or not it's "active" after the first day, I don't know. I assume it does accumulate over the course of treatment and reaches it's highest concentration on the last day of treatment.
When I saw the dead guppy, first thing I thought was "ammonia spike," but the ammonia/nitrite is 0. The test is working accurately, confirmed by testing the 30g which is fishless cycling.
What about temperature? I have read article after article on these types of infections. Some say increase temp, some say to decrease it. Some say columnaris is gram-positive while others say it's gram-negative. If they can't agree on these details, how do I even know if the treatment info I'm reading is accurate?
So, I brought the temp back down to their normal, which is 78-79F.