Hello. Here is what I'm treating. Columnaris 20 gallon long 6 Harlequin Rasboras 3 Panda Cories Dates of Deaths 7-5-2017: One cory in a holding tank while changing substrate 7-6-2017: Another cory and our betta 7-7-2017: Another cory Today is 7-9-2017, and the remaining fish are seeming to behave more normally. Find it odd that 3 cories died only a week roughly after adding 3 new ones. I'm wanting to start a quarantine practice after this. Some may find this thread familiar. It may be. We were treating for ick because that's what the "wonderful PetSmart employee" told us. Then we figured it out to be columnaris with some help. Then out of desperation started a new, more natural treatment. Less than 10 hours in I was not comfortable with it. I had also heard about the Kanaplex/Nitrofurazone combo. So today, I did a 75% water change to remove the 19 teaspoons of salt. I also finally found Jungle Fungus Clear Fizz Tabs at Walmart of all places. After the water change I dissolved 2 tablets in a container with some aquarium water, and poured it in. As some of you can probably guess, my water looks like a bog now. Greenish yellow and not very pretty. It's hard to see this in the picture. From my understanding the nitrofurazone in this med should help stop the spread and reproductive rate of the infectious bacteria. I also have Kanaplex on the way from Amazon. This is where I start asking questions. Being that I have not had a death in two days, and the fish are starting to eat again and act normally, do I really need to dose this antibiotic? From my understanding, this is what actually kills the columnaris bacteria. However, you're not supposed to dose unless needed because it can cause kidney damage otherwise. So should I use it with the second round of nitrofurazone in 4 days or not? Additionally, what all exactly do I have to do after treatment? Do I have to disinfect the whole tank? If so how? Or can I do 2-3 50% water changes and put the carbon back in the filter? Am I missing anything? Just can't wait to actually get this over with, move my inverts back in, set up a quarantine, and get some new fish going.