Tank cleaning?
 

I'm fixing up an old tank. The person that had it before (my dad) had siliconed pieces of slate rock to the back. There are still marks from the silicone and I was wondering what I can use to try and get them off. A lot of the marks can be seen but not 'felt'. Also the tank just generally needs all of the glass cleaned up. what should I use?

Thanks

diluted bleach will work, just make sure to rinse the tank well after. For the small silicone bits, just take a razor blade to them and they should come off easily.