Some are even really rare and for their certain features, many have been selectively bred. Others are hybrid of even more than one species.
Common tropical fish that need fresh water include bichirs and redfish; catfish; characins and other characiformes, cichlids, cyprinids, killifish, labyrinth fish, live-bearers, loaches and related cypriniforms, neotropical electric fish, pufferfish, rainbowfish, spiny eels and gar among others.
Species like the Discus Fish are best kept by themselves in a tank as they tend to be too timid while others are highly aggressive that they are not compatible to live with others in the same aquarium such as the Oscars, varieties of Cichlids and Jack Dempseys. Green Swordtail, Variable Platy, Southern Platy, Bala Shark, Red-Striped Rasbora, Malabar Danio, Tiger Barb, Rosy Barb, Gold Barb, Cherry Barb, Marbled Headstander, Serpae Tetra, Garnet Tetra, Glowlight Tetra, Cardinal Tetra, Blue Tetra, Bloodfin Tetra, Iridescent Shark, Upside-Down Catfish, Platies, Swordtails, Mollies, Killifish and some types of Labyrinth Fish can live in a community.
Highly recommended for first timers are Goldfish, Siamese Fighting Fish, Gray Bichir, Ornate Bichir, Reedfish, Amazon Sailfin Catfish, Walking Catfish, Black Phantom Tetra, Black Tetra, Buenos Aires Tetra, Cave Tetra, Emperor Tetra, Glowlight Tetra, Neon Tetra, Serpae Tetra, Sunshine Peacock Cichlid, Eureka Red Peacock, Blue Dolphin Cichlid, Afra Cichlid, Electric Yellow Cichlid, Malawi Eyebiter, Auratus Cichlid, Chipokee Cichlid, Blue Johanni Cichlid, Aurora, Red Zebra Cichlid, Cobalt Blue Cichlid, Kenyi Cichlid, Giraffe Cichlid, Julie Cichlid , Masked Julie, Lyretail Cichlid, Jewel Cichlid, German Ram, Texas Cichlid, Cherry Barb, Gold Barb, Rosy Barb, Sumatra Barb, Malabar Danio, Pearl Danio, Zebra Danio, Striped Panchax, Guppy, Black Molly, Sailfin Molly, Dalmatian Molly, Variable Platy and Green Swordtail.
Having been successful in taking care of the types mentioned above, for the next challenge, you might want to try adopting the following species which have special needs: Spotted Raphael, Black Neon Tetra, Bleeding Heart Tetra, Congo Tetra, Green Neon Tetra, Rummy-Nose Tetra, Blue Lyretail , Dwarf Gourami and Black Ghost Knifefish that are sensitive with their environment and are prone to diseases.
Brown Ghost Knifefish that feeds on live food; Marbled Hatchetfish and Black-Winged Hatchetfish that can jump out of the tank; male Three-lined Pencilfish that tend to really defend small territories; Marbled Headstander that fight among each other especially in small groups; Two-Stripe Dwarf Cichlid that are more comfortable in pair in a 40 gallon tank; and finally, the Angelfish that definitely cannot live with tetras as it find them annoying.
Meanwhile, the types of Red Bellied Pacu, Blue Discus, Red Discus, Threadfin Rainbowfish, Congo Pufferfish, Giant Freshwater Pufferfish, Green-spotted Puffer, Chinese High Fin Banded Shark and Electric Eel are quiet difficult pets in terms of feeding, breeding and maintenance.
According to size, fish may be as small as 1 inch to as big as 35 inches or more. Tetras, hatchetfish, pencil fish, danios, rasboras, headstanders, guppies, mollies, rainbowfish and Angelfish American Cichlid can grow from 1.5 inches to 5.9 inches.
Beechers, Redfish and the Two Spot Glass Catfish can be 14 to 18 inches. On the other end, Lake Tanganyika Cichlid Boulengerochromis Microlepsis can be as large as 35 inches while a bagrid catfish like the Asian Redtail grows 51 inches. The growth of fish is especially considered in choosing the size of tank.
Fish tanks require tropical elements fairly needed by the fish such as water temperature, lighting and plants. Most species of fish in their natural habitat live in regions with water temperatures of up to 80 degrees Fahrenheit.
It would be safe to maintain water temperature between 60 to 90 degrees Fahrenheit depending on the variety of fish. For example, while goldfish is a well-known freshwater aquarium, it actually is a kind of cold-water cyprinids that it requires cooler temperature than the ideal tropical temperature of 80 degrees.
Variants of goldfish include the Black Moor, Bubble Eye, Butterfly Tail, Calico, Celestial Eye, Comet, Common, Fantail, Lionchu, Lionhead, Oranda, Panda Moor, Pearlscale, Pompom, Ranchu, Ryukin, Shubunkin, Telescope Eye and Veiltail.
Lighting in a fish tank should be monitored as it emits heat and is influential in the biological cycle in the new habitat. It is advisable to turn-on the light for at least eight hours a day for a healthier fish. Meanwhile, they need plants as shelter, spawning area and as part of their diet.
To not provide the tropical feel in an aquarium has its consequences like discoloration of fish, abnormalities in fins and gills and worse, fish disease or expiration.