Hello and welcome! What a wonderful idea! We are between ponds at the moment, and I think I miss the frogs the most. We have our goldfish in 2 large outdoor tanks, but I think they are too high for the frogs & toads to get in.
Agree that water in motion is the way to keep your water fresh and oxygenated. Where do you live and is your pond in shade or full sun and is it lined? With a pond that shallow, I’m going to predict that you will have evaporation issues, especially during the hotter months. This means that you’re going to be adding water often — please be sure that you dechlorinate the water — and that the temperature of the water may get too high for the survival of any critters.
Have you seen the solar fountains they sell for bird baths and small bodies of water? If you have enough sunlight, something like this might work well to keep your water moving. It should also help keep out mosquitoes. Something like this....
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