What the hell do you fish people do about moral-free fornicating cannibal fish?
I had a small tank with a couple of guppies in it. Three months later I have three small tanks with varying sizes of fishlets and a shameless hussy living (for the moment) in a bottle of water.
If I put the female in with her largest sons she gets shagged silly in about 30 seconds. If I put her with her smaller offspring its feeding time at the zoo.
What to do?
AnimalsTaiwan has lots of hungry kitties. Please help feed our stray kitties!
Just don’t take the small ones out. They eat them pretty fast. Don’t give them too much food when the tiny ones appear. Usually there are only 4 or 5 that survive the feast.
Noooooo! The tiny ones are the cutest. The whole point is to NOT have them get eaten. Is there really no way?
Can’t you get condoms for fish or something?
Sure. Get condoms. Put the fish in them. Give them to any AnimalsTaiwan representative…
Now you know what Oscar Wilde was talking about. (Never drink water…)
Ugly ones (female) in one tank, pretty ones (male) in the other. Problem solved.
Or do what I did - use a new coal filter to purify the water - all the little bellies up in less than an hour. 
Yeah, tank divider to control the number of fish that get to mate. then get some pirahnas to deal with any overrun. Or a cat. Pirahnas don’t look much (silver dollars are more attractive) but they are easy to keep.