I have Pseudacris crucifer tadpoles collected tadpoles from Michigan wetlands three times this this spring, and every time they died withing 12 hours. I understand that they are sensitive to temperature changes, but this most recent time (Saturday the 28th) they did not undergo any big temp changes. I keep them in containers like soft margarine tubs, etc, in water from the wetland from which they were collected. This last time they were extremely small tads, so I do not think oxygen was depleted.

Any idea what's killing them?