i have an 850 ltr thats 224 us gallons . i have 8 discus , 2 sorubim lima , 1 Platydoras costatus , two armored catfish (not corydoras) , two flounders i think is Cynoglossus feldmanni , 1 panaque , 4 Hoplosternum thoracatum and about 45 Moenkhausia pittieri . I am looking for a fish , preferebly from south america witch live close to the surface . it must not be larger than 40 cm 8 inches . a predatory fish is preferred . If anybody can help me , that would be great .