chris
i keep loads of eels. the fire eels are by far my fav. they do grow quite big and quite quickly. my biggest one is about 55cm at the moment, he lives in a 1.5 meter 550 liter tank and will be moved to a 2.5 meter setup in a couple of weeks. they are wonderfull fish to keep and do well in a non aggressive comunity, however the fact that they can top out about 100cm needs to be taken into consideration.
they love a sand bottom while small (they love to dig and will spend most of their time completely burried with only the mouth or head sticking out), as they grow they tend to stop digging and like hiding under wood or in caves. they are also very strong and move big pieces of wood by themselves therefore loose rocks piled on top of one another should be avoided. the are also quite succeptable to skin disease so avoid anything with sharp edges that they can hurt themselves on.
when small feed it blodwoorm, as it grows switch to earthworms and when big enough you can try beefheart or ox liver.
i am not too hot on conversions (from SA and we use Liters, meter etc.) etc but you would need to have something in the range of a 4 to 6 foot tank to keep it in, but you would need to upgrade to accomodate it when fully grown. they normally top out at about 60 to 90 cm that is 2 to 3 foot in aquaria.