Two weeks ago I decided to up the numbers of my schooling/shoaling species so I bought 4 cardinal tetras & 3 otos (I already have 7 cardinal tetras & 3 otos). I set up my quarantine bucket with a cycled sponge filter & heater and properly acclimated the fishes, it was past 10 in the evening then. The morning after, one of tetras died and I just scooped it out and disposed it. Chalked it out to maybe stress and not some serious disease. But a few hours later, another one again died and the two remaining tetras are showing the symptoms of columnaris. So I immediately dosed some medicine (sera baktopur is the only one I got, kanamycin & nitrofurazone is not available in my place) and hoped for the best. One didn't make it the next day and now I'm left with one cardinal tetra & the 3 otos. I'm planning to finish the one month quarantine period to be sure, but my question is if the remaining fishes survive the whole ordeal, is it safe to add them to my main tank? Wouldn't they be carriers of the disease? How about the equipment (fishnet, bucket, filter & heater), should I sterilize them or just dispose them after?