Probably a stupid question?

Here's an answer,
http://www.aquariacentral.com/forums/showthread.php?t=126049
For a short time, it wouldn't be a big deal. However, if you continue to do this, it will build up over time.

Any uncoated metal will leach into your water. Some are less toxic than others. Lead is toxic to just about everything. And, if you have any objects in your tank that are able to absorb lead, they will continue to leach out lead after you have removed the weight(s).

Excellent alternatives are, rocks, clips with a suction cup (that's what I use), spear it on a fake plant, decoration. The possibilities are endless! ;)
 
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