What The Heck Happened

[MickeyMousePlaty216]

Today I decided to add some fresh water to my tank.
I had did a water change last week, but the water
was evaporating a little quickly.

fifty-five gallon
My tank temperature is 80
every thing is okay, low ammonia

Some fake plants, some live plants

7 male guppies
8 platies 1 male rest females

I notice after I put the new water in the tank that my female
hifin platy top fin was split in half. It looks like someone cut
a perfect line in the middle of her fin. I notice it ten minutes
after I add the water. she was perfectly fine early.

I have very little aggression in the tank from one of the females
in the tank but she has been very less aggressive when I added
the new females and she never picked on the hifin.

The temperture raised to 82 for about ten minutes but thats it.

I was wondering if It will ever grow back? and what could have
cuased this to happen to her? and will it ever happen again?

I am worried that she might be endanger of another fish in the tank
please help me solve this problem.

 

[helterskelter]

Your water is very hot these fish are happier at 70-74f

Sure it will be fine in time though

 

[Jonty]

What do you mean by 'low ammonia', cos it has to be 0