Decorations for my fish tank. The stuff is sanitized by the way and my fish haven't died yet from the plastic. Gonna get backdrop made
with a mushroom cloud. 
I've used hot-melt glue, polypropylene horticultural fleece, acrylic sheet and polyurethane car-sponges in my aquariums, and some of my creatures are kept in big polypropylene storage boxes filled with water. I've yet to find a plastic that's noticeably harmful to them, though I give any plastic items a good rinse before I expose my creatures to them. The polypropylene storage boxes come with some kind of water-based lubricant on them that's probably a mould-release agent left over from the manufacturing process or a lubricant to prevent them from sticking to each other during storage and transport, and I spray them with the hose until they stop making the water cloudy and slightly foamy, and until the plastic feels tacky rather than slippery. The polyurethane sponges that I use as filter media also have some kind of residue in them that I wash out of them.
