The actual medication that is recommended for BGA is Erythromycin. Maracyn is just a trade name for that. Maracyn-TC is actually tetracycline. That's a whole different class of antibiotic. It might work, but personally, I'd stick with E-mycin.
It works pretty well at lower than the usual recommended dose too. I dosed about 10mg/gallon (the usual dose is 250mg/10 gallongs) and it worked beautifully after only 2 doses.