Despite comingfrom relatively small localities when compared to marine fishes, tropical freshwater species offer a diverse choice both of variety and in breeding methods.
Body shapes vary according to the need to adapt to correspond to water conditions - fast-flowing, still and deep, shallow and crystal clear. Because conditons in these waters are subject to seasonal changes too, freshwater tropicals have developed a tolerance to these changes with the result that most can be kept in the widely differing water qualities which emerge from our taps.
However, the biggest attraction of freshwater tropicals - apart from their visual appeal - is that not only can most be bred in captivity but also there are diverse methods of breeding to understand and appreciate.
Freshwater tropicals are generally divided into two distinct gropus: livebearing species and egglaying species.
Livebearing fishes do just that - they 'give birth' to miniature, fully-functioning replicas of themselves. The fertilised eggs develop inside the body of the female although in the majority of cases the young fish do not receive nourishment direct from the female during this gestation period. Fishes such as female Platies, Swordtails, Mollies and Guppies can give birth to more than one brood without re-mating with a male and, of course, colour varieties within a species will interbreed indiscriminately.
Egglaying species breed differently: during spawning, eggs are normally released by the female into the open water where they become fertilised by the male's sperm. Depending on species, some, or none, parental care may be exercised; with the majority of egg-scattering species (Barbs, Danios etc) the adult fishes are more than likely to eat their newly-laid eggs immediately after spawning.
Egg-depositing fish, such as most cichlids, prepare a spawning site (a rock, leaf surface or even upside-down on 'ceilings' inside rocky caves or overturned flowerpots) on to which their eggs are first laid then fertilised.
It is usual then for both fishes to protect the fertilised eggs up to hatching, and often well beyond, by keeping other fish away from their chosen nursery site.
How about the Killifishes? Here, egg-hatching can be delayed up to several months so that fertilised eggs (buried in mud) can survive the annual drying out of the fish's natural streams.
Fertilised Killifish eggs can also be stored in semi-damp peat-moss for several weeks before re-immersing in water activates the hatching process; obviously, this characteristic makes it easy to send Killifish eggs to other interested aquarists!
Bubblenest breeders (Siamese Fighter, Gouramies) prepare another type of spawning site - a floating nest of bubbles at the water surface into which fertilised eggs are laid and also guarded.
Because members of this group often have auxiliary breathing organs in their head, they can cope with depleted oxygen levels but don't make this the reason for neglecting to keep their aquarium conditions at their best!
Mouth-brooding cichlid fishes (most African Rift Valley Lakes species) take parental care that little bit further with the female incubating the fertilised eggs in her throat cavity; after hatching, the free-swimming young still return to her mouth for safety.
These fishes are quite happy to be kept in very hard water - it is just like home to them - but make sure there are enough rocky retreats in the aquarium for all the fishes, they can get quite territorial.
You can see from the above that there are plenty of challenges and interests laying in wait for the new fishkeeper!
Aquarium Size & Water Preparation
Heating, Filtration Systems
Setting-up and Running-In
Fish & Plants
Feeding, Water Management & Disease
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Last updated March 27, 2002