Tetras are of the pirhana family..... there are also some that are "fin
nippers".... I would ahzard aguess that this is your problem... the males
are choosing who'll be top dog and are nipping each others fins..... is it
just the dorsal fin that is affected?

Tiddleye
"Debbie"  wrote in message
news:cmn49vgthqbgifip3ui7q7557q8odfj5bq{at}4ax.com...
> Can anyone tell me if the male black phantom tetras top fins are
> supposed to be "split" in the middle??
>
> This is really worrying me as we have 9 phantoms, 3 males 6 females
> that we have had about a month and as the males are growing larger
> whenever they "display" their fins to each other and turn coal black
> the top fins are now split in 2 or 3 pieces which I did not notice
> before. They look a little raggedy as well.
>
> The females do not have this but their fins are much smaller. The fish
> are acting fine. I read about fin rot and don't really think that is
> what is wrong but I do not know. There are no white edges or see
> through parts and it does not look like the fins are getting smaller,
> just shredding.
>
> I have a 29 gal established tank which I do 10-20% water change
> weekly. Last time I tested water about a week ago I had 0 ammonia, 0
> nitrites, and about 40-80 nitrates. Hard to tell on that one due to
> color. The other fish in the tank are 9 Cardinal tetras and 3 pepper
> cories. So no other fish are harrassing the phantoms, other than the 3
> males frequently chasing each other. We have two filters, a hang-on
> and a ug with a powerhead. Both are turned down to the point of not
> creating excessive current, so the fish are not fighting to stay in
> place. The ug is going to be removed in a few weeks (or sooner) in an
> attempt to better control the nitrates. The tank has been set up going
> on 7 or 8 years, the ug came with it when new.
>
> Any suggestions appreciated.
>
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