any got a care sheet on them

Try this one Care Sheet - Common Snapping Turtle

i need to no how big the tank have to be when thay get big

For a single fully grown adult a 6' x 2' x 2' is probably about the minimum, if you wanted to keep two together it would need to be a lot bigger or they'll almost certainly fight, which they might do anyway regardless of the size of tank, so be prepared to have two setups of this size.

Have you actually seen adult snappers in the flesh? Before committing yourself to one I suggest you try to find someone who has one and go and see it, this is quite a specialised animal and is really not suitable for beginners.

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