An older brochure states that Maracyn should be used for Columnaris. It also states that Maracyn is most effective against gram-positive bacteria. Several online sources have stated that Columnaris is caused by a gram-negative bacteria and that erythromycin is almost useless. If they are correct, should I use Maracyn-2? If you think they're wrong, please point me to documentation supporting your contention. Thanks.