They do not require a lot of room to swim as they will only swim if they are stressed.
Did you do any research before deciding to try one? This is not an animal that you can be successful with on a whim. Different species have different specialized diets and require constant feeding throughout the day. The water has to be very stable and especially with no nitrates.
If you "think you can keep one good", what do you plan to feed it? Are you aware that most do not actually feed on the commonly available foods? Note that they can take up to a year to starve as noted by the apparent limit of how long most end up keeping them before they fall apart.
Next time you should probably ask the questions before buying such a demanding animal. It's an animal that requires a tank to be built for it, rather than hoping it will thrive in an average system.