Nice. Looks healthy. Don't be surprised if it loses its bubbles. They often do. There is really no known reason for bubbling vs not. Don't forget to feed the GBTA. I recommend silversides once a week. It is probably hungry and it is good to check the feeding response anyway.
Also, it took my female Occ. 3 months before it took my RBTA as a host. Another 3 months before the male joined her. So it could just take time. BTAs are not their natural host, so it can be hit and miss.
How long have the clowns been together? The picture makes them look about the same size. Has one started dominating yet?