well, i was putting the full dose of melafix for my 2.5 last week each day, but without doing any water changes, as the instructions said not to change the water until the 7th day. but then i read cation's post and realized i needed to do 100% water changes every day before i added the melafix so as not to overdose the poor guys. both of my boys were fine both before when i was overdosing them, and now that i've been changing the water every day. hm, maybe it depends on the bettas' different immune systems?
all i know for sure is that melafix has worked well on bb's mangled fins.
i have 2 filters in this tank (without the active carbon as per instructions on bottle), so that may have diluted the melafix during the week i wasn't doing water changes.