Was considering whether or not I should use some LEGO sets to make cool underwater themes in my planted community tank. I've read that it should be safe because it's a hard plastic, assuming that stickers aren't used on them.
Maybe some Lincoln logs for more rustic look?
Might have to soak the wood pieces in mesh bag with a stone to hold it down, to see whether the log's are releasing tannin's or whether they are painted.
Imagine with children's habit of placing thing's in their mouth's, that the wood pieces would not be too harmful after a good soaking, but it is only speculation.
Hmmm,maybe a small cabin with moss roof.and....