3 years ago i dug 2 ponds in the summer/autumn with my bare hands! (ok ok, i used a shovel too!) one with a few fish, and another that it cascaded into with just plants n stuff in. a pump in the lower pond feeds the upper pond, and so the cycle continues... 2 years ago, we put a load of frogspawn in the top pond, but the fish ate it all, or so we thought!!! last year we seen 2 frogs, and a small dollop of frogspawn in the lower pond. this year we have at least 8 adult frogs. several weeks ago we had a shedload of frogspawn and cutting the grass has become a bloodbath! theres little frogs everywhere! lol so, i dunno if some survived from the first batch, or it they found it themselves, but they are doing quite canny now you should hear the noise they make when it rains!