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Fish watching could be very relaxing to the hobbyists. But knowing the behaviors of the aquarium fishes you keep could make the watching more pleasant. There are fishes that are bright and colorful but the predatory nature could ruin the friendly atmosphere in the aquarium increasing your blood pressure at the same time.
The careful selection of the fish in the aquarium is quite essential. The aggressiveness and the predatory nature of some fishes can be dangerous to the life of the other small colorful fishes. If left alone in the tank, these could be great pets, hence should not be written off from the list of favored aquarium fishes.
Few aquarium fishes that eat other fish
Some breeds show dominance and aggression in their behaviors making them not a preferred one in the community tank.
Red-bellied Piranha
The red bellied Piranha is a colorful and attractive fish decorating your aquarium. However, the aggressive nature makes it a poor choice for the communal one. This breed should be left alone in the tank with minimal handling.

Arowana
Arowana fish are large pets that live up to 20 years giving opportunities to the fish owners to bond with. The aquarium specimens grow to about 30 inches while those in the wild can grow nearly 4 feet in length. The fish needs space to jump, swim and move around and prefer the whole tank for them. At times these could be intimidating as well as they have teeth everywhere, even on their tongue.

Puffer Fish
This is another breed that prefers to live alone. These come in a wide variety of colors and patterns. These are the gems in the aquariums. These could be very small in size of an inch and can grow to as long as 3 feet depending on the species.
However the hobbyist has to be careful while placing these in the tank. These should not be housed with any other carnivorous species as they are quite toxic to most predators.

Killifish
Killifish may not be very aggressive with other but one can still not allow the males killifishes to stay together in the same community tank. The male ones can be aggressive towards each other. The beginners in the field of fish keeping should be careful while placing the species in the tanks.
Keep a pair of Killifish in the species only tank. But if you are keeping a group together in a larger tank, then be sure to provide a lot of hiding places in the tank.

Pipefish
Pipefish form the unique group of fish that can be kept in the aquarium by experienced keepers. These are very often overshadowed by the seahorse but are liked more by the hobbyists wanting to add newness to their tanks. Their long snouts are capable of sucking in small crustaceans, plankton and other live food like the shrimp.
The larger ones sometimes eat up the smaller fishes making them a no for the community tanks. Proper care needs to be taken about the diet during their transition from wild to the captivity.

Crowntail Beta
The Crowntail Beta fish adds flavor to the aquarium. Whilst they come in a variety of colors, the most prominent ones are the darker shades of blues and reds. The origination of the fish is from the Siamese fighter fish. These show aggressive behavioral patterns not liked by many breeds of fish. However, they can co-exist with the peace loving varieties that dwell at the bottom of the tank.

Basic knowledge about the behavioral patter along with diet and tank requirements can make their existence in your aquarium quite a fun pass time.