Common Minnow - Breeding in Captivity

Breeding in Captivity

The Eurasian minnow breeds well in cold fresh water aquariums, but it is rarely sold as an aquarium fish. They need a good supply of oxygen (some air bubblers do fine), a reasonable current (which is often provided by the bubblers if they are good strong ones), and a gravel bottom. It is not clear what size works best although smallish (0.5 cm each) works well. Clean water helps and so do plant life and general good quality aquarium conditions. Breeding begins around late May when the fish become noticeably more active, and the fish begin to change colour. The females don't change their colour so much, more the shape of their body; in fact the colours seem to fade if anything except for the fins which become slightly more red. Their body becomes more deep set toward the abdomen, which area also starts bulking out. Although the changes in the female are small, the changes in the male are huge. First of all, the difference in the shades of colour on the fish become stronger (dark gets darker, light gets lighter), and the fins, throat and some other areas redden. These colour changes strengthen as the fish gets closer to breeding. The body becomes much bulkier, and the gills become very pale with iridescent light blue patches towards the bottom and below. This contrasts with the now very dark body. Later the scales on the lower half of the body begin to stand out more and become slightly gold-lined. All these strengthen as time passes on. All the fins, especially the dorsal, start to stick out more; this happens in both sexes. The males begin to chase females around, rubbing their sides against them, and this becomes very frenzied and aggressive towards the mating. Mating happens when this behaviour reaches its climax where the female releases the eggs and the male fertilizes them.

Fertilised eggs promptly sink to the bottom and into the gravel. The other fish will start eating the eggs and picking at the gravel to find them. The male will then ferociously guard them for a period of time. A few days later the eggs will hatch and the fry will emerge. It is very important to have much plant cover for the fry to hide in as the adult fish will try to eat them especially if underfed and if not much other live food is given. The baby fry feed on small organisms called infusoria and algae. To grow infusoria for feeding just get a jam jar of pond water and run it through some cotton wool or muslin to get out any larger predatory organisms like daphnia which will eat the infusoria and add hay to the water. Leave it for a few days in a dimly lit room at about room temp. and when you next look you should see lots of tiny white dots in the water which, if looked at under a microscope reveal to be lots of types of infusoria in their millions. these can be fed to the fry by adding them to the tank. To get more just add some of the old water containing the infusoria to cooled, boiled tap water with hay and repeat the other procedures. As the fry grow their diet changes. When they reach about half an inch they can be fed small organisms like daphnia or cyclops. These can be obtained by dragging a net through water where they can be seen or they can be purchased from aquarium dealers. Soon the fish will eat the same food as the adults and will quickly grow.