Nice catch....5x2x2.....Go for a centerpiece.....Single Midas Devil...Of course start off with 5 individuals when 1-4 inches.....Chances are high you will get a pair out of it...But from personal experience, sometimes males turn on their females and are killed.....So I would stick with a single Midas Devil....Ordering from Rapps a wild male is another option....
As for filtration:
mechanical
(2) AC101's
or
(2) Emperor 400
chemical and biological
(1) canister filter--->RENA Xp3 or Fluval 404
or
(1) DIY wet dry filter....