You better let the filter run for a while before you have another swim in there. Those little buggers crap in the water.. and lots of it... we had a female living with our other pet duck, looked after her from a 2 day old chick till she got old enough to be able to fly. One day she just flew off, hopefully to join a flock of the same kind.
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Yes I am an agent of Satan, but my duties are largely ceremonial.