Why he never switches off
A male guppy's courtship is not misbehavior; it is the entire strategy of a livebearer whose life is short and whose breeding window is now. He displays his tail, sidles into the sigmoid curve in front of a female and attempts to mate many times an hour, every hour the lights are on. With a harem spread across a planted tank, that energy disperses and females graze, rest and feed between approaches. When only a female or two shares the tank, that same energy lands on the same bodies without pause — and harassment stops being a description of his behavior and becomes a description of their whole lives.
Fix the ratio, then fix the layout
The arithmetic comes first: at least two females per male, and three is kinder in a small tank. More females means each one is courted a third as often and gets genuine rest between encounters. Then give them somewhere to spend that rest. Floating plants and tall growth reaching the surface are the females' refuge, because a male hunts by sight and broken sight lines end chases; a thicket a female can slip into sideways stops pursuit the way open water never can. Feed in more than one place so a guarded female is not choosing between hunger and harassment at the single food point.
Rest, separation and the male-only option
If one male stays relentless in a well-planted, well-ratioed tank — some simply do — somebody's address has to change. A divider or a separate rest tank lets the females recover condition for a week or two while the male stays behind, and sometimes the pause resets the group. Removing the male permanently is cleaner still: an all-male guppy tank has some sparring and display but no one is chased to exhaustion, since males posture at rivals rather than pursuing them relentlessly. What rarely works is adding a single new female to absorb attention — she arrives stressed, becomes the freshest target, and the original problem simply gains a victim.
What exhaustion looks like in the females
Learn the cost signs so you act before damage: a female who hides all day and emerges only to snatch food, fins held clamped and tight, a body thinning despite feeding, or a fish resting on the bottom or at the surface out of the male's routes. Stressed females also drop fry early and fall ill more easily, because constant pursuit suppresses the immune system. A female showing wounds, a fuzzy or white-edged sore, or one who has stopped eating altogether should be moved to quiet water of her own, and if she does not recover appetite within a day or two, contact an aquatics-savvy veterinarian — exhaustion deaths in guppy tanks are usually recorded as mystery deaths when the cause was courtship all along.
Checking whether the balance holds
Judge the new balance across a full week of feeds rather than one hopeful evening after changing numbers or planting. Note whether the females feed openly, rest inside the planting and hold their condition across several days. For a borderline week, put a follow-up question to KinsLe's Kimmy; she answers using the KinsLe Answers library.