LESSON: TROPICAL FRESHWATER FISH
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The largest segment of the aquarium fish industry is the
freshwater aquarium fish sector. Major groups include
the poeciliids and the egg - layers.

• Poeciliids (guppies, mollies, swordtails, platies)
These are also known as livebearers because they are
viviparous. (A few other nonpoeciliid fi sh are also
viviparous.) They are prolific, with many line bred
strains. These fish are often relatively inexpensive,
although certain strains may be high priced.
The so-called egg - layers encompass all other fresh water aquarium fish. Major groups include the
following:

• Characins (tetras) — These are active, schooling fi sh
that usually stay in the upper water column. Some
species may be a bit aggressive and nip fins or chase
tankmates. Most make good members of a community
aquarium. This group also includes the piranhas, which are not good for the community aquarium.
• Tropical Cyprinids (barbs, danios) — These are active,
schooling fish that usually stay in the upper water
column. Like the characins, they may be a bit aggressive and nip fins or chase tankmates. Most make good
members of a community aquarium.
• Anabantids (bettas, gouramies, paradise fi sh, etc.) —
These are generally peaceful fish that are good candidates for a community aquarium, except for the
popular Siamese fighting fish, which, although aggressive toward conspecifics, are shy toward unrelated
species. Anabantids breathe air by using an accessory
organ modifi ed from gill tissue (labyrinth organ).
• Cyprinodonts (killifishes, topminnows) — These are
generally small, often brilliantly colored fish, many of
which have short natural life spans (e.g., annual fi sh).
They are often shy among other types of fish and do
best in a separate aquarium. There is usually marked
sexual dimorphism.
• Catfish ( Corydoras, Pimelodella, Plecostomus, etc.) and
Loaches (clown loach, kuhli loach, etc.) — These are
generally peaceful, bottom - feeding fish that are useful
as scavengers to keep the gravel clean. Most make
good members of a community aquarium.
• Cichlids (freshwater angelfi sh, discus, oscar, African
rift lake cichlids, etc.) — These are a popular group of
fish that include a wide range of species having diverse
behaviors. Some make excellent members for a community aquarium (e.g., angelfish), while others are
extremely territorial and can only be kept with equally
aggressive species (e.g., oscar). Some species have
marked sexual dimorphism.
• Oddball fish (archerfi sh, piranha, freshwater butterfl y
fish, etc.) — These are species that are occasionally kept
by aquarists as novelties. They include a diverse array
of species.

Hey guys! Could you please tell me which tank size is the best for my Kuhli Loach fish? Thanks in advance for your answers!