I have a terrapin. He doesn't bite at all. He is one of the ones with a bit of red on, we've had him for about 4 years now, he has not grown that much. He started about the size of a 2 pound coin, but now he's about as big as the palm of my hand.

We did keep him in a tank, but when he got a bit bigger we put him outside in a small pond-type thing. I wouldn't put any fish or anything in there cos they have a tendancy to eat the fish, even if they are bigger.

If you do ever put it outside make sure you put lots of plants in the pond, as well as rocks and wood for him to swim under, so the seagulls stay away. Or even put a net over the top to stop animals getting in.

I wouldn't worry about it growing huge for a good while, if it grows at the same rate as mine you'll have to wait at least 10 years to have it the size of your hand.

I think as long as you keep it well-fed and don't bother it much you won't have a big problem with biting... I certainly have never had a problem.

From personal experience, I find that they like:

Deep water, but with an easily accessable dry area above the water, preferably with sun AND shade (mine likes to sunbathe)

As a treat, but not too often, some thin ham and small prawns (but not too many, I think they are quite salty)

Plenty of underwater obstacles and plants.

Oh and I wouldn't advise getting more than one. Terrapins don't need company - They like to live solo, and there is also the risk that with a few of them one becomes dominant and eats all of the food and such the others will die.

Hope I helped