At full size this character will need at least a 55 gallon tank and preferrably one that is a bit wider than the standard 55. Fortunately it takes years for them to reach full size (there are records of Polypterus
living over 30 years in captivity).
is one of the smaller bichirs, one of the most active, and the most commonly available. It will reach a mature size of about 12 inches. They are available from PetCo and PetSmart as 'dinosaur eels' (though they're certainly NOT eels). I bought 5 baby ones at PetSmart a few months ago (all under 2 inches)....the largest is now a little over 4 inches. They're not the most colorful bichir by any means but in my opinion they're one of the most personable.
Here's one of my 'babies':
Polypterus palmas palmas
and Polypterus palmas polli
are other good options. Again...both are relatively small (12 inches) and quite active, though not as commonly available as P. senegalus
Here's my Polypterus palmas polli