We've always had frogs in our garden, even before we had our koi pool. So after I completed it I built them a small one of their own. Koi pools are no good for frogs other than for hiding in the folds of the liner or in the pump sump during the winter. There's nowhere to safely lay any spawn, any on the bottom would be eaten by the fish and any in the bottom drain or the pump sump would get flushed away during purging. As it only has an overflow, over the course of a year it gets full of dead leaves which I always remove before the frogs get "at it" in the Spring. This detritus could harbour all sorts of nasties that could affect the health of the frogs, they can absorb stuff through osmosis. It's only a small pond , but it's a pain to clean out. Fortunately, now the koi pool has gone I hung onto the small pump I used to pump the waste in the pool sump to a house drain. So no getting down on my hands and knees, just dropped the pump in the pond with a hose connected to it and filled several buckets. The mole wrench was to stop the hose flying everywhere. The pond water makes an ideal fertilizer for our acid loving plants. I finished off with a net and then my wet n' dry vac. I've a problem with tthis pond now, as it is no longer level. As I did with the koi pool, I started with a concrete collar before I dug it out. With a collar you can get it perfectly level. This is how it looked in 1986. I later moved the lamp and the second acer inexplicably died. Over time the acer palmatum I planted nearest the lamp grew and for the last ten years the roots have been pushing up the collar on that side and the edging stones on top, so now the overflow on the right is much higher than the left hand side of the pond. So the pond looks lopsided, as if I filled it to cover the overflow pipe, the water would escape on the left-hand side. What I should do is remove the edging stones and the concrete collar and start again. But I can't be bothered. I don't want to disturb the roots of the acer. There's no plants in this pond now as anything in it dies because it is in the permanent shade of the acer which nearly covers it in the Summer. This doesn't seem to bother the frogs, there's a "ladder" of rocks at the far end for the young frogs to use when It's time for them to leave. Some years the whole surface of the pond has been covered in spawn, every clump looks different. There's not been as much since the koi pool got filled two years ago.