Possible copper use in used tank (re-sealing)

[birdy]

I acquired a used tank, that seems in pretty good condition, the side silicone was a bit rough so I went ahead and removed it and re-siliconed it.
My question is about the bottom, the silicone seems to be tinted blue, now at first I thought it was just the silicone, now I am wondering if perhaps it is from copper being used in the aquarium. I plan to set this tank up as a reef so I want to be sure no copper is going to leach from the silicone. I just think it is a bit odd only the bottom silicone was discolored, not the sides at all.
What would you do? I am thinking I should just re-seal the bottom so I don't have to worry about it, but the bottom seal looks fine and I hate to screw with something that is fine. My other thought is to put some water in the the tank, let it circulate with a powerhead for a while and test for copper.
Oh I thought I would add it is a small tank (24LX18WX24H) so it is not a huge deal to re-seal it.

 

[acrylic51]

The blue tint on the bottom could be due to the previous owner using Malachite (spelling)...When this medication is used it does tint the water blue and will stain silicone as well....Have you leak tested the tank since removing the silicone on the sides?
I would put water to it and run your pumps and test for copper, but if copper is present will probably be released rather slowly.......Make sure if you reseal the bottom that you completely remove all the silicone and clean the area really well to be resiliconed before resealing.....If not properly cleaned silicone won't form a good bond and will leak eventually