I have a QT setup for inverts/corals that has never seen meds and it has a 150 watt halide over it. I try to make them wait two water changes, which I do weekly, so they usually get two weeks and if all looks good, on the third week, they get tossed in the DT. The water change thing is just to see how they react to any sort of stress. There is such a lower risk of transferring parasites with clams, so it's really an "observe and use your own judgement" sort of thing.