08-28-2010, 09:10 PM
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The number of fish that any aquarium will comfortably and safely hold depends upon the water volume, type of fish, size of fish, water parameters, and physical environment (plants, wood, rock according to the fish's respective needs). There are no "numbers" that work every time. In your tank (30 litres or 8 gallons), 12 Ember Tetra would be fine, with a group of 5-6 pygmy corys. Whereas 12 neons would not. For small tanks, small fish. And fish differ from species to species with respect to their interaction, numbers needed to avoid stress, behaviour to other species, etc.