FIMO, lead (came) and fish tanks

In an effort to be cheap, I’ve been considering making my own structures for my fish tank. I’ve thought about using FIMO clay (similar to Sculpey) and/or having a friend do a stained glass structure.
Do I have to worry about the FIMO releasing anything toxic into the water? I assume it becomes just a plastic once baked.
What about the stained glass? Stained glass uses solder which is mostly lead (you can get solder that is only 20% lead but it’s still lead).
Should I stop being a cheap bastard and just go buy the tacky-ass stuff at the fish store?

Have your friend do the stained glass, but connect it together with clear silicon sealer. ( I had a chess board made of different colored glass squares all held together with the above…it was bendy, but it worked.)