On reflection I'm not sure that having them clear out the sponge is necessarily a bad thing. Part of the blurb about apiguard is that the bees carting it out of the hive aids the distribution of the thymol vapour.
If I'd been more prepared, it might have been useful to compare mite counts between colonies that removed the sponges and those that didn't but in truth the level of detail on the mite drop went as far as "1,2,many, lots!".
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