BBA can be very difficult to eradicate--I speak from experience. BBA likes too much light, too little CO2
and overfeeding. Check out other threads about BBA.
If you have plants, you may have to treat the plants in quarantine with Excel Flourish and blackout for a period of time. Also the lights may be too much. Try a blackout and or interrupting the photosynthesis time--4 hours into...dark...2 hours on. A timer is helpful.
If you have no plants, take the coral out and scrub with toothbrush and bleach then rinse, rinse, rinse and declorinate.
It might be good to blackout the aquarium for a while (3 days) to starve any other spots of BBA out that were too small to notice.
Also, Chinese Algae Eaters are not effective on BBA. The only known BBA eaters are true Siamese Algae Eaters. They do get big though.