Just curious why you have gone from an LTA to a Sebae and now a BTA??? I am assuming the tank is new and I understand the desire to have clowns associating with a nem but you will have a very hard time keeping any nem alive in a small unstable system.
Frogspawn/Torch/Hammer corals are about as likely to host clownfish as your BTA is, BTA's are not a natural host for A. Percula or A. Ocellaris and as such the clownfish are normally unlikely to associate with them right away if at all. I had similar clowns with 4 BTA's for almost a year with no luck, used a natural host and had association in less then 30 minutes.