The Common Scat (Scatophagus argus), also known as the Green, Red, or Spotted Scat. A popular brackish fish, these are commonly paired up in large aquariums with Monos as they tend to break up any dominance issues between adult Monos. Easy going fish, but fairly robust in size (6-8 inches maximum). Best kept around 1.010 specific gravity, they are adaptable and can even be put in fully marine conditions.
(Source: fishtanksandponds.co.uk)