ive use ethromycin before. while it is one of the meds that most fish seem to tolerate it did kill 2 of my cories. dont know if I spelled that right. ethromycin also is not cheap esp if you have a large tank. I have been experimenting with black outs as they are almost free to do and so far seems as safe as ethromycin. results may vary.
now that my bga seems to be gone, I plan to add more circulation. this seems to be one the common causes of bga. I have researched and tried a hydor nano 240.. it is a small circulation pump. this turned out to be too much circulation even for my 55gal. I believe many people who run this small hydor use it for reefs or plants but for bettas it is prob too much unless you have hard scape or something ro provide sheltered areas.
next im going to try a small internal filter or something adjustable.