1) I've never had a problem with metal in fake plants myself.
2) Bend at a 45 degree angle and place in substrate. You can put rocks on top if you wish. I use a 2-5" layer of substrate in most my tanks, sloped higher in the back.
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Did you quarantine them at all? I have read dyes are a possible issue as well and it seems they are a bigger issue than metal rusting.
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