[acidWarp]

If the tank is very new the silicon may not have been completely cured. Also there could have been a bacteria growing on the inside of the glass that bloomed once you added water. These are long shots but possible

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I doubt that is the reason why it smells. As George and others have said, I also believe the smell is a result of the tank not being cycled properly before introducing fish.

If the tank was only set up 48 hours ago, the smell is the likely result of ammonia and other waste from the fish that is failing to be broken down due to a lack of established bacteria in your filters. I suggest you get some ammo-lock and bio-spira immediately and read about how to properly cyle your tank.