Nearly 40 years ago when I built my house, I installed a 1300 gallon cistern next to it. All along, it has fulfilled many yard or garden needs. Several weeks ago I opened the hatch and noticed a tree frog swimming inside. No harm done there. It was likely eating mosquitoes anyway. 

Checking a few weeks later, I began to see the result. There were hundreds, maybe over a thousand tadpoles swarming about.

Within 3 weeks some were getting legs, then loosing their tails.

I put a few cedar shingles on the water to provide more habitat.

Then I placed a wood ramp leading them to the open hatch.

Some began climbing the inside walls of the tank..

They averaged only about a centimeter in length.

Now tiny hoppers are emerging from the cistern, with multitudes yet to go.

So far, they look like they’ll be happy in their new home!