Ok, i have that dratted columnaris in one of my tanks, 20g tall, 12 guppies. Ive treated this tank with nitrofurazone, 2 doses, 4 days apart, then 3rd nitrofurazone dose, with kanaplex, then kanaplex 2 days after, then water change,then nitrofurazone with kanaplex. Had multiple deaths. Big water change, found on testing water my cycle has been knocked out. Added salt. Lowered temps to 74. 4 days no symptoms.. then bam loosing about 2 fish daily again. Dosed last night with kanaplex. Only had a 4 day break. What on earth do i do now? Ive separated guppies with symptoms to a breeder box. I hope someone has some good ideas becsuse im running out of them. Help me please!