When fish stress fish - can this be prevented?

[HopeGR]

I'm still learning about my aquarium. I'm puzzled by one thing - do all kind of fish stress out fish, or is it specific breeds? Probably the answer is 'all.'

Started with guppies, now I see it with platys. I have balloon mollys and it seems to me those can endure more pressure.

So I have 8 mollys and 2 platys in a 20 gallon. I bought two bumblebee mollys and platy in early November. Just a few weeks ago, the platy started with mating with one of the bb mollys to the point of stressing her. Found her dead Saturday. Now he went after my 2nd bb molly, stressing her to the point she is twitching and hiding. By stressing I mean swimming side by side or going next to her and making her jump, and simply following her wherever she goes. I am certain I'll find her dead by the end of the week if not sooner.

Both bb mollys were active, eating, and quite happy for 2 months, coexisting, and then the platy just started this maybe 2, 3 weeks ago.

So is it just the platy and guppy that do this kind of attack? I still haven't seen my balloon mollys get this weak with their mating, and I do prefer them the most. It just bothers me that they die this way so suddenly! Can this be prevented (without separation?)

[charliebankston]

No, all males pester and harass the females for spawning. Some just do it worse than others. Once, my female convict got out of the tank and into the hang on back filter to hide from the male. I'm not kidding. In the course of one night she was so beat up and ragged I thought she would die (she's still living, but not him). I couldn't find her in the aquarium, and my wife found her inside the filter. Crazy

[HopeGR]

Wow, that's sad about your fish. I'm doing my best to feed them a well balanced diet, hoping this will help. She seems better this morning but the stressing continues.