Not trustworthy! and hence endangering your fish. If you could beg some visqueen from a construction site or steel a kiddie pool while their napping the fish would really appreciate it and the news anchors could have fun with the story.
Go on freecycle.org in your area and ask for a pool if you don't see one there, If you can find a big enough one you don't care if it leaks since you'll be cutting it up anyway.