You don't need wild caught clowns for your BTA to host. If you put a maroon or a tomato or a clarkii in with the BTA, you will likely find it goes to the anemone within days, if not hours. If you can buy captive bred, then do. Wild caught clowns are much more likely to have parasites. BTA's are natural hosts for around 12 species of clowns. Unfortunately they are not natural hosts to perculas or occelaris, some of the most commonly available and sought after clowns in the fish trade. However, in captivity, occelaris and percula will often go to a BTA. Tomato, maroon and clarkii are commonly available clownfish that are natural symbionts with BTA's.