Fish were observed twice daily for clinical signs associated with
columnaris disease. Fish unable to maintain neutral buoyancy were considered moribund
and were removed for sampling. Dead and moribund
fish were removed from the tanks daily, and samples were taken
from the necrotic lesions and cultured on selective cytophaga agar
(Hawke and Thune, 1992) containing 5 mg/mL neomycin sulfate and
200 U/mL polymyxin B. If present, a maximum of three moribund or
dead fish was were sampled from each tank daily. Cultures were incubated
at 28 °C for 48 h and then scored as being positive or negative
for growth based on colony morphology