non-aggressive fish
Catfish
Danios
Gouramis
Guppies Hatchetfish
Loaches
Mollies
Platies Plecostomus
Rasbora
Swordtails
Tetras
White Mountain Cloud
What makes a fish semi-aggressive is the reaction to a hostile or negative situation. Something has to aggravate the fish for them to act out or display aggressive behavior, otherwise they will be on their "best behavior." Examples of semi-aggressive or lively fish include, freshwater sharks, angel fish, barbs and gouramis.
Angel Fish
Barbs
Flying Fox
Freshwater Sharks
Gouramis
(its ok to mix non-aggressive and semi-aggressive fish)
If fish are territorial, or are only compatible with their own species, they are classified as aggressive. These fish will protect their own territory and will harrass, chase, and pick on other fish. Fish may only show aggression to those that are smaller. Some of the most common fish that typically show aggressive behavior are cichlids and bettas.
Cichlids
Bettas
Environment
To thrive in aquariums, tropical fish need a certain level of comfort: places to hide, areas to explore, and sites for breeding. Nothing provides this healthy environment like aquarium plants.
Bottom Huggers
These fish are usually scavengers. Some just prefer to stay in caves or among rocks near the bottom of the aquarium.
Examples:
Catfish, Red Tail Shark, Clown Loach, Plecostomus
Middle Schoolers
These fish like to swim in the middle of the tank. Not all mid-range fish are schoolers. Fish that school like to swim in groups of six to twelve of their species.
Examples:
Swordtails, Sunset Variatus, Gouramis, Guppies, Tetras.
Top Lovers
These fish like to swim near the top of the tank, near the surface of the water. Some top lovers are prone to jump out of the tank, so make sure all openings are covered!
Examples:
Siamese Fighting Fish (Betas), White Cloud, Danios, Marble Hatchet, some Gouramis.
All Levels
These fish like to swim in all levels (layers) of the tank. For a dramatic community display aquarium, consider the number of fish you want to see in each level of the tank. A large school of one species of fish will look spectacular!
Examples:
Cichlids, Rasboras, Bleeding Heart Tetra, Barbs, Mollies, Platies.
Source:
http/www.diveintofish.com/tank/
Regards
Darren