Unfortunately no Maracyn II will not treat it but Maracyn will. It is a fungus infection and Maracyn II is totally ineffective for those. The other things that will treat it are: Jungle Labs Fungus Clear Tank Buddies, Maracyn Plus (probably the very best choice as it specifically says Mouth Fungus), and Maroxy (very harsh..not unless a last resort). I would say that the Jungle Labs Fungus Clear is the least strong and cheapest, but Maracyn is the most likely to be used later if something else comes up. The Maracyn Plus is great because it is a liquid and easy to dose and you just give every other day for 3 doses and then repeat if the job is not done, but expensive.
Don't beat yourself up really bad over the tank thing..we all get lax now and again. Just clean the tank up really good before you start any medication or you will be wasting any meds you do use. Please do keep us informed of her progress and do not be surprised if she will not eat for you while she is sickest as their mouths HURT with this stuff.
My first
betta had it while he was cycling his own tank before I found Fishlore.com and had no idea what the
nitrogen cycle was all about and he did not eat and when I contacted a Vet friend of mine who likes fish he told me the basics and what to do and why he was not eating. Tell Sarah I am sorry she is sick and we will keep her in our prayers and thoughts.
(yes I do pray for the sick fish)
Rose