Nipping

I just noticed one of my cardinal tetra lost 1/3 of his (her) tail fin. We just cleaned the tank on last Friday with 40% PWC. (0, 0, <10)

It is hard to believe to have fin rot and/or fin nipping in our community tank.

Size: 36G Bow
Fishes: 2 Male Guppies, 9 Rasboras, 5 Neons, 2 Cardinals
Parameter: 0, 0, <10 (Very Clean)
Setup: 4+ Months,
Recent addition: Rasboras (Over 2 months ago)

Neons and cardinals have been scholled together well and do not have any issue so far.

I'd like hear opinions from the experienced hobbyist. (If needed, I will upload some pictures when I get back home.)

Thank you for the reply.
1/3 of tail fin is missing.

ct-death said:

Is their a piece missing, or torn, or split? It wouldn't be unheard of certainly, especially from the guppies IME, albiet rare.

Click to expand...

Thank you!!! CT

That' is the only possibility I guess. We just separated male & female guppies due to increasing population around 2-3months ago. Two male guppies are usually actively swimming / chasing each other. But they don't bother tetras or rasboras.

I do not want to put the injured cardinal to QT tank because QT is very busy with 12 corys. He swims fine and eats well. Do I have to move him to QT?

Thank you!!! CT & MSjinkzd

I will change water again today.
(I will put him in QT only if I can identify any secondary bacteria infection (With Maracyn treatment) or if his fin is not recovered in 2 weeks (With Malafix treatment).)