When good tetras go bad

[poikilotherm]

Hi all,

I have a bit of a detective mystery on my hands. I just went away for a week (very nice vacation on the Oregon coast, thank you for asking) and when I got back, one of my Harlequin Rasboras was missing an eye. Ack. Something always happens when I go away. I had someone I trust feeding them, but not watching for this sort of thing. The injured rasbora is behaving normally, and eating. Everyone else looks fine, except for a cardinal tetra with a slighly frayed dorsal fin.

My slightly overstocked 29 gallon tank contains the following presumed innocent fish: 4 corydoras julii, 1 upside-down catfish, 1 bristlenose plec, 1 Apistogramma panduro, 1 Apistogramma cacatuoides, 1 Microgeophagus ramirezi.

The other fish, potential suspects, are: 3 clown loaches, 1 angelfish, 7 other rasboras, 1 Geophagus juripari (Satanoperca leucosticta), 2 cardinal tetras, and 1 head-and-tail light tetra.

It's a mystery. The clown loaches are just playful happy little (2") guys, the angelfish has only ever got mean with other angels. The Geophagus only bites gravel. The rasboras seem a little nippier with each other than usual, but the h-t-l tetra (my oldest fish) has been more obnoxious recently too. I think he might be the culprit.

My questions:
Has anyone seen any (older) tetras turn rogue?
What are your recommendations for (non-[acronym:eb020abb7a="quarantine or quart depending on context"]QT[/acronym:eb020abb7a]?) wound infection preventative treatments?
Any other thoughts?

I (or rather, my wife) would like to avoid setting up the [acronym:eb020abb7a="quarantine or quart depending on context"]QT[/acronym:eb020abb7a], but if it's the only way, I'll do it. I may also sell the h-t-l tetra back to the pet store if he starts messing with my Apistos or my ram...

[acronym:eb020abb7a="Thanks in Advance"]TIA[/acronym:eb020abb7a] for any ideas.

[mpdt]

I ahve had customers tell me that their danios have turn cannibal on them and killed the other fish in their tank.
If you tank is overstock then that is your main problem. Also to you use any salt in your tank ? If not, then this will help, and keep your temp. under 78 degres.

[ferret]

The cories should actually be on your suspect list. I've heard multiple horror stories from various people of having fish disappear, and then they investigate and find underfed cories are the culprits, ambushing and eating sleeping fish.

Since you were away for a while and someone else was in control of the food, I wouldn't entirely rule that out. I don't know how common that behavior is though or if its specific to a certain species.. I've only kept Bronze and Green Emeralds. ([acronym:032b6fb112="By the way"]btw[/acronym:032b6fb112], GE's are WAAAY more active and cool than the Bronzes)

[AquaBear]

You know, come to think of it, I've noticed MY Zebra Danios exhibiting some aggressive behavior. One of my platys has a little chunk out of it's tail fin, and some times even after the food is gone, they're still running around, bullying the other fish. My tank isn't over-stocked, and these are all supposed to be "peaceful" fish.

--AquaBear

[poikilotherm]

Thanks- I'll keep an eye on the corys. I do use salt (~1 Tbsp per 6 gals) routinely, and keep my temp at 78. I'll just sit and stare at my tank for a while to try to understand what's going on! I may need some night-vision goggles to catch the nighttime chicanery.

[ferret]

I do know that SALT is a bad idea for cories, and maybe the clown loaches as well. I'd dropped this practice.. The other fish will be fine without it and it can possibly irritate or injure the cories.

[Menagerie]

Oh my! I would also put the upsidedown cat on the Most Wanted list. Although, they usually only eat what fits in their mouth.
Where did you go on the Oregon coast?

[mpdt]

We salt are cory's and loaches everyweek at my [acronym:1468fb8322="Local Fish Store"]LFS[/acronym:1468fb8322], and they are doing fine.

[mpdt]

We salt are cory's and loaches everyweek at my [acronym:98e98e607a="Local Fish Store"]LFS[/acronym:98e98e607a], and they are doing fine.

[Menagerie]

A low level, such as 1 TBSP per 10 gals or so, should not have an adverse affect on the cories or loaches. When you are treating for ich, where the salt is more concentrated, there may be problems.