The silver dollar (Metynnis argenteus) is a tropical fish belonging to the Characidae family which is closely related to pirahna and pacú. Originating in the Tapajós River basin in South America, this somewhat round-shaped silver fish with slight red-tinged anal fin is mostly found in tanks kept by fish-keeping hobbyists. It will grow to a maximum length of 5.5 inches (14 centimeters).

The silver dollar is a peaceful schooling species that spends most of its time in the mid- to upper-level of the water. Its maximum lifespan is more than 10 years. An egg-layer, the adult fish will spawn around 2,000 eggs. This breeding occurs in soft, warm water in low light.

Silver dollars natively live in a tropical climate in the sides of weedy rivers. They prefer water with a pH of 5–7, a water hardness of up to 15 dGH, and an ideal temperature range of 75–82 °F (24–28 °C). Their diet is almost exclusively vegetarian and in captivity they will often eat all the plants in a tank. They will also eat worms and small insects.

The Common Hatchetfish or River Hatchetfish (Gasteropelecus sternicla) is a tropical fish belonging to the Freshwater Hatchetfish family (Gasteropelecidae). Originating in the South America in the Peruvian and middle Amazon, the Guianas and Venezuela, it grows to about 2.5 inches (6.5 cm). The fish gets its name from its relatively large protruding belly which resembles a hatchet.

The River Hatchetfish is a schooling species best kept in groups of five or more that spends most of its time in the top-level of the water where it searches for food. The fish can be peaceful or aggressive. Its typical lifespan in captivity is around five years.

These Hatchetfish natively live in streams in a tropical climate and prefer water with a 6.0 - 7.0 pH, a water hardness of up to 15.0 dGH, and an ideal temperature range of 73 - 81 °F (23 - 27 °C). A carnivore, their diet consists of annelid worms, insects, and crustaceans. The fish will often jump out of the water to catch small aerial insects. Because of this behavior, they may jump out of aquarium tanks.

The Mexican tetra (Astyanax mexicanus) is a freshwater fish of the characin family (family Characidae) of order Characiformes.[1] [2] The type species of its genus, it is native to the Nearctic ecozone, originating in the lower Rio Grande and the Neueces and Pecos Rivers in Texas as well as the central and eastern parts of Mexico.

Growing to a maximum overall length of 12 cm (4.7 in), the Mexican tetra is of typical characin shape, with unremarkable, drab coloration. Its blind cave form, however, is notable for having no eyes and being albino, that is, completely devoid of pigmentation; it has a pinkish-white color to its body.

This fish is reasonably popular among aquarists. This is especially true of the blind cave form.

A. mexicanus is a peaceful species that spends most of its time in the mid-level of the water above the rocky and sandy bottoms of pools and backwaters of creeks and rivers of its native environment. Coming from a subtropical climate, it prefers water with 6.0–7.8 pH, a hardness of up to 30 dGH, and a temperature range of 20 to 25 °C (68 to 77 °F). In the winter it migrates to warmer waters. Its natural diet consists of crustaceans, insects, and annelids, although in captivity it is omnivorous.

The Mexican tetra has been treated as a subspecies of A. fasciatus, the banded tetra, but this is not widely accepted.

Species name: Hyphessobrycon Flammeus

Synonym: Hyphessobrycon flammeus

Common name: Flame Tetra / Von Rio Tetra

Family: Characidae

Order: Cypriniformes

Class: Actinopterygii

Maximum size: 5 cm / 2 inches

Environment: freshwater

Origin: South America

Temperament: Peaceful

Company: Hyphessobrycon Flammeus (Flame Tetra) is suitable for community aquariums.

Water parameters: Temperature 24-27°C / 75-79°F; pH 6.0 – 8.0

Aquarium setup: Hyphessobrycon Flammeus (Flame Tetra) prefers a well planted aquariums with lots of hiding places and some free areas to swim on. They also prefer dimmed lighting. Hyphessobrycon Flammeus (Flame Tetra) are very undemanding and can be kept in most water conditions as long as extremes are avoided. They should always be kept in groups of 10 fishes or more.

Feeding: Hyphessobrycon Flammeus (Flame Tetra) accepts flake food..

Breeding: Hyphessobrycon Flammeus (Flame Tetra) is easily breed and produce up to 250 eggs. The eggs will hatch in 24-50 hours. The parents eat their own eggs and they should therefore be removed from the breeding aquarium as soon as the eggs has been laid. The eggs wil not hatch if exposed to light.

The Colombian Tetra comes from Colombia. It is also know as the “Columbian” Tetra, the Blue-Red Columbian and the Red Tail Mirror Blue Tetra. It was known by the scientific name Hyphessobrycon ecuadoriensis and more recently as Hyphessobrycon columbianus, which more accurately describes its Colombian origin. It has only been available in pet stores since 1995 and has become a very popular tetra. The Colombian tetra has a band of blue across the upper body with red in the fins, especially in the caudal fin. The lower body is silvery.

The Colombian is very hardy and is a good beginner fish, however it is fairly aggressive and should only be kept with more nippy, active and aggressive tetras, such as the Serpae, Blind Cave, Buenos Aires and the Silver Tip Tetra. They are definitely not good companions for smaller tetras and guppies. Colombians will be happier and show better colors when kept in groups of 6. They appreciate a well planted tank, but the will eat plants. Colombians will eat flake foods, freeze dried bloodworms and brine shrimp.

Males and females are difficult to distinguish by coloring. The female is larger and broader, especially when laden with eggs. Soft, slightly acidic water is best for breeding and lighting should be greatly dimmed. Pairs should be separated for more than a week before breeding and fed a variety of foods. Tetras have adhesive eggs, so fine leaved plants or spawning mops should be used to catch the eggs. Colombians will spawn multiple times over a period of days. The parents should be removed after spawning. The fry are very small. Fry should be fed infusoria and the finely ground flake foods.