The pond is definitely clearing. For over a month, it has been a murky green, created by growth of single celled algae in the water. It seems that was a temporary phenomenon. The growth would have brought about by a flush of nitrates in the water. And my inclination is to think it was from the waste created by all the adult frogs we had in March, possibly as many as forty over the month. The pond is now clearing as the nitrates have been used up. We hope.