I have had the same problem and found that the broad leaves of the Water
Hyacinth were under water fall or filter outlet and were splashing the water
out of the pond. Check and see this may be your problem . They will move
around in the wind and currents.
Hank

"C.Champ" wrote in message
news:SPDBa.773894$OV.711914@rwcrnsc54...
My pond is one of those prefabed plastic ones and I have had
it since last year. Everything has been great with it this
year until last weekend. I bought 20-25 small Water Hyacinth
and put them in and now the pond loses 1-1 1/2 inches of water
per day. Is it possible that the new plants are drinking that
much. We haven't done anything else. Thanks in advance for any
help.
CC