A couple first of my breeding projects weren't very successful. Among dis-satisfactions were the size of swordtail progeny which is smaller than their parents. I also noted that youngsters proceeded early sex maturation, which could be the reason for the reduction of growth rate or even cessation of body growth. There're couple things that control the maximum potential size of my swordtail could reach: - Inheritance - Diet - Captive environment - Early sex maturation A- Inheritance: I usually see Kohaku koi swordtail at medium to small size when purchasing them from Aquabid breeders and local fish store. As far as I was told Koi swordtail is among the youngest strain created in late '90. It is clearly that this strain was a hybrid. An origination of Platys ancestor as well as long time interbred could have contributed to its small size in comparing with other swordtail strains. So, a cross breed with "giant" swordtail would help to improve the situation. Nevertheless, crossbreeding a Koi swordtail individual to another strain of Swordtail would significantly decrease the quality of bi-color band. And "Koi" coloration is still mysterious to me. B- Diet: The fishes are fed with Brine shrimp twice a day, and Hikari pellets for livebearers during the day. C- Captive environment: At the moment, I could only keep 20 gallon tanks in my recreation corner. So the population is often around 20 swordtails each tank. Water change is done weekly at 80-90% and all tanks are treated with Aquarium salt to promote acclimation. The temperature is maintained at low optimal 70 - 72 Fahrenheit. D- Early sex maturation: I believe that social environment has some effects on early sex maturation. From my observation, late mature males usually develop bigger body size; but these males in my tanks were usually those being bullied by a dominant character which made them often hide away for a long time until they were bigger and stronger to fight back. Then I found interesting piece of journal mentioned that "females and males adjust their age at maturation in response to visual cues of male sexual ornamentation in the current environment: females matured earlier, whereas males matured later if all the mature males seen had large ornaments" (Walling et. al., 2007). So, I designed that as early as a male is sexed out, I placed him in the male tank and hoping that the aggression of dominant males would slower his maturation due to suppression. Without any female in the male tank, it seemed that dominant males were also less aggressive after all. That way, females would be preserved to be virgin, avoid sexual harassment from males, and fully developed until they are ready for brand new breeding projects. - Males and females are separated as soon as they are sexed out. - The effect of having a dominant male may help suppress the sex maturation of the others, thus leaving more time for the other males to fully develop. - Females would also have more time to develop if avoid sexual harassment from male swordtails. Citations and References: Green swordtails alter their age at maturation in response to the population level of male ornamentation Craig A Walling, Nick J Royle, Neil B Metcalfe, Jan Lindström Biol. Lett. 2007 3 144-146; DOI: 10.1098/rsbl.2006.0608. Published 22 April 2007 Females matured earlier in the long-sworded treatment than in the short-sworded treatment, while the converse was true for males. Females from the long-sworded treatment were smaller than females in the short-sworded treatment, whereas males did not differ in size between the treatments. (Walling et. al., 2007)
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