In a 40 breeder, if you dont get the convicts maybe a smaller cat, but not gonna get to see much out of it. Cats are mostly nocturnal
As i said before, these are very hard to get in my place.dwarf pike cichlid, Crenicichla compressiceps or Crenicichla regani
Having a list of conditions like this makes it difficult to pinpoint a single good species. Exodon tetras fit the bill best if you can find them where you live. But if you think about it many larger tetras are extremely vicious eaters and fairly easy to keep. How about some of the deeper bodied tetras with Apistogramma cichlids?-Active
-Agressive/Voracious eater
-Durable