I recently purchased a second hand 3ft fish tank and decided to re-seal the base so I was confident it was water tight. I used just what silicone was in my tool bag as I was unaware of such thing as "Fish Safe" silicone.
The product I used was "Bostik Bond-Flex 100HMA Silicone Sealant Black"
Bostik Bond-Flex 100 HMA Sealing Silcone
It is around the bottom of my tank which is now buried in substrate, sand and plants. So I am reluctant to remove all this unless the silicone really does pose a problem for my future fish.
Any advice would be greatly appreciated.