Why are almost all of my guppy offspring male?

Question

Hello, I started breeding guppies over a year ago, and since then, they have started at least 3 new generations of offspring. The problem is that around 80 percent of the offspring are male, and they are constantly swarming around the females. I know the normal male/female ratio is supposed to be 1 male for every 2 females, so thats just messed up that I have so many males. All of the fry were raised in the same tank as the adults, and some of them got eaten. Is it possible that all the females got eaten somehow? Or is there an environmental factor having effect on guppy gender such as temperature or water pH?

Answer 1

Color enhancing food that contains hormones will yield fish that are disproportionately male in many species.  Try to avoid any foods that advertise "color enhancing" even if it just says they have krill and vitamin c as the main color additives.  They can often have hormones not on the label, which provides them a competitive advantage in the marketplace to unwitting consumers.   I often find that plain sinking shrimp pellets are good for my adult guppies when breeding them.

You may also be suffering from basic genetics and a god hand... In humans, the male has a predetermined mix of x vs y s*x chromosomes in their dna.  I suspect you're just seeing that play out in your fish, only nature isn't taking its course & killing off the lot who bear a less fit set of genes since you're micromanaging their existence and preventing them from dying.