BIG surprise when I got to school this morning. We had a huge storm last night, lots of damage and power out all over town. The power at my house has been out for 8 hours so far. At school I go out to check the pond and found it nearly empty, just enought water for the fish. Water was trickling out the biofilter at the output spout and it was overflowing over the side. After taking the opportunity to clean the bottom of the pond and the pump I found a piece of furnace filter was blocking the spout on the biofilter. That's why it was overflowing and emptied the pond.
I filled the pond part way because I don't have any additives to put in the water to clear out the chlorine. I will add more later, but we are expecting more storms so I will let it completely fill with rain water. I also rearranged the stuff in the biofilter so there is netting in front of the spout so flow won't get blocked.