Warnings:
Some plastic containers leach toxins that can kill fish. When using plastic, change water often to remove toxins, especially if moving over long distances.
Tips from eHow Users:
Plastic buckets can kill aquarium fish by A A.
I learned this the hard way. I lost two special fish. Plastic wading pools can also kill fish.
http://www.ehow.com/how_7155_relocate-aquarium.html
This also applies to all new materials added to an aquarium - silicone, PVC, flexible hose, acrylic and other new items even glass.