Cardinals And Neons Dropping Off Daily - Whodunit?

[monkeyhanger]

I wish that our lass hadn't gone out and replaced all our dead NTD neons with cardinals - they just seem so much more fragile than the neons ever were.

1 a day is dying now. Each day, one seems to have its tail fin gone and it's dead or dying when i get in from work, with no signs of infection - i'm sure one of the other fish is having a nibble.

The Betta has never bothered the neons before they were sick - why start on the cardinals now?

I also have 6 Platys, 4 Cory Sterbai, 6 Glass Bloodfin Tetra also.

Is it most likely the Betta out of the above list of suspects?

It's not just the small cardinals affected - some are almost 2" long and are still losing their tails.

The bloodfins are totally intact, not a piece off their fins.

I think i'm going to give up on these weak, overbred fish. Might get a few more platys in different colours, or top up the bloodfins.

 

[LauraFrog]

Can you get a photo of one of the dead fish? Hard to know what's causing this... I guess you could remove the betta for a day or two and see if this stops it. Generally when we tell people not to keep bettas with tetras, the problem is likely to be the tetras stressing the betta by damaging its fins, not aggression from the betta towards the tetras... most bettas are fairly peaceful with other fish that are obviously too big to snack on.

 

[monkeyhanger]

The dead fish are gone - if I see another one i'll photograph it.

The cardinals have the clear part of their tail fin gone, but no sign of fungus or infection. The red "V" at the start of the tail fin is still there. There is no other damage to the cardinals, they just go one at a time on a daily basis. Lights on or lights off, there's no other fish that seem to be harassing them or taking a bite.

The Betta is really placid, I picked that one because it was in the neons and corys at the LFS and all tank inhabitants were cohabiting nicely, in a tank less than 1/2 the size of my own.

 

[monkeyhanger]

Think I know the culprit. One of my 6 glass bloodfin tetras regularly leaves the group at the top of the tank and heads low where the platys, corys and cardinals are. That bloodfin was nudging one of the cardinals a lot last night.

I had 2 further cardinal losses yesterday - one was dead but uneaten and complete, and I found just the head of one of the smaller cardinals - I should have 3 left, but can only see 2. Nothing happens overnight when the tank is pitch black. In the morning, everything is as it was the night before. But from going to work at 7:30am to coming home at 5pm, that's when a cardinal ends up on the menu. Tank lights are on 1pm to 10:30pm.

Not having any more cardinals!

Can anyone suggest something colourful thats a bit hardier, can stand it's ground but unlikely to start nipping my betta? Nothing large either - i'm trying to keep everything under 3 inches, compatible with Corys, Platys, Betta and Bloodfins.

Did see the glass bloodfins swimming with a similar glass tetra at the local LFS, almost the same as the glass bloodfins, but they had copper coloured eyes and no blood red tail. Maybe they'd be good as a mixed shoal?