Medaka Rice Fish: Detailed Intro
Medaka rice fish is also called Japanese rice fish. The variety of Medaka is Yellow Princess.
Medaka is the cultivated form of the rice-fish Oryzias latipes native to irrigation ditches, rice fields and other still waters throughout Korea and Japan.
They are a kind of killifish but the show just how closely killis and most common livebearing fish are related.
Their body shape is very similar to guppies and even the way they reproduce. Guppies and their relatives are not livebearing in the same way as mammals.
Guppies still lay eggs but they are retained inside the female. They take no nutrients from the mother.
Rice fish haven’t quite got the ‘retain the eggs in the body’ down. The eggs hang close to the female’s body when they emerge and the male fertilizes them at that time.
Eggs are usually laid in small clusters every 20 days at first light. Usually, a few hours after they are fertilized, they will be brushed off on plants where they stick until they hatch.
Male rice fish do not pester the females as much as male guppies do as they only breed at a certain time of day.
They are considerably thinner than the females but only slightly more colorful in the cultivated forms.
In the wild, rice fish are all uniformly grey/tan with blue eyes and just a hint of blue iridescence.
Japanese breeders have been working on these fish so now there are blue, red, whites, yellow, black, long-fins and a sparkly diamond form. They are perfect fish for unheated tanks or for growing outside in tubs.
The medaka rice fish I bought a couple of weeks ago has been doing well. This is the second female to be carrying eggs since I got them.
The eggs will be brushed off on some plants where they will hang until they hatch (or until the rice loaches find and eat them which is more likely)
I had to run to work so I could not take time to save the eggs…but this should happen about every 20 days.