how long does it take for clown fish to adopt toadstool corals?

That is usually unpredictable. if the purchases were recent, all are still adjusting to the tank, and adjusting to each other is best held off until down the road. If the clown fish have never been around coral or anemones before, it generally takes longer. The adoption is gradual. The clowns have to desensitize the coral so that it does not react to them which takes time. If they rush it, a clown could end up dead and eaten by the coral just like any other non-immune fish. They seem to know this and take their time before adopting the coral.