Amongst loads of other rubbish left for us when we moved here was an old babies bath. Once I have bunged up a small hole I intend sinking it in the "wild" area and filling it up with water to see if I get anything taking up residence. I saw it somwhere on here, I'll let you know how I get on.
P.S. By wild area I mean of course, somewhere I haven't got around to working on yet
Edit: I've found the thread. It is by Bluemoon in the thread childs sandpit thing.