Fish loss, only my Corys

[Walker Anderson]

Hi, I was wondering if anyone could shed some light on what I might have goiing on in my tank. Set up is 30 gal. Med planted. Med-High light. Penguin 150 biowheel, Fluval 204. Tested twice over the weekend. 0-ammonia, 0-nitrite, 7.0 Ph, .2 Nitrate. Tank has been stable for quite a while now. Over the weekend, all 4 of my Corys died. 2 on Saturday, 1 Sunday, and I found the last dead this morning. My 5 Black skirt tetras and 10 neons are fine. When I got the corys out I checked each for any obvious signs of death. They all looked uninjured. The only commanality was their fins where straight out from thier body, like wings. Other than that, I could see nothing. Gills looked fine. No ick, or bleeding. Complete mystery to me, but these were some of my favorites in my tank.

I have a UV sterilizer currently UPS ground on time tracking for delivery tomorrow. A little too late possibly, but I would like to find the root cause of this. If anyone can shed some light on what would only kill my Cories, I would appriciate it.

Thanks,
Walker.

[aquarob]

I have no idea what killed your Corys, but I wanted to say I am sorry for your loss. My Corycats are my favorite also, and if they died I would be most upset. If it only affected your corys, i would suspect some kind of heavy (i.e. heavier then water) chemical poisoning. Perhaps a heavy metal that wasnt neutralized in your last water change? Make sure to treat your water with a good conditioner. I highly recommend Prime, by Seachem. Detox's pretty much everything from heavy metals, chloramine, chlorine, ammonia, nitrite, you name it. Smells terrible so be careful not to spill it on the carpets. Heh.

Again, sorry for your loss. Cory cats are great, and in my experience very hardy little guys. Dont give up on them. Take care.

[Roan Art]

Just a thought, but wondering if you have a few anaerobic pockets that the cories might have dug into?

Not sure I'm explaining myself too well or using the right terminology :) What I mean is that with a planted tank we tend to lightly clean the surface of the gravel and sometimes pockets of debris can form. It's possible, I think, that if your cory school ran into one of those pockets it could have poisoned them. I've found a few nasty spots in one of my tanks and when I tried to clean it out, the nitrates shot from 0 to 80ppm. Bad juju.

OG or someone else can explain better than I can. I think they'll know what I'm getting at :)

Roan

[Walker Anderson]

Thanks for the replys guys. Thinking of it, on Friday night I did a 30% water change and vac'ed the open spots pretty good. I did use Prime, and yeah the sulfer smell from it is pretty rank. My substrate is a mix of gravel on bottom, laterite in middle, and sand on top. I suppose I could have stirred up a pocket of nastiness. I think I will wait a while before I restock any bottom dwellers. I will miss my fattest Cory who had a habit of drifting in the one airstone's bubbles, riding them to the surface, shooting back down to the bottom and slowly drifting into the bubbles and letting them push him to the top again. Sometimes he would do it for 30 mins or more. Oh, well. This gives me some thoughts on making a different vaccing schedule, and not wait so long between, or maybe do like I used to and use an old antenna from an old tv. Rabbit ears style and extend it so I could swirl the sand around a bit. Got a bit lazy on that. Seems like lazy cleaning on my part may really be the answer. Once a week may not be enough for the substrate I have in there. Or at least a mid-week stirring up of the sand.

[Roan Art]

Nod. Wait for OG or RTR or someone with more knowledge to confirm what I've said.

One way you can combat it, especially in a larger planted tank, is with one or two strategically placed powerheads or water pumps. That way you can make sure there are no dead zones where the water doesn't flow. I'm putting one in the side at the back of my tank to make a small current that will help keep things moving. I'm also moving a few rocks around so that water can flow through easier.

FWIW I've lost a few cories in my older tank and I suspect it's for the same reasons. One of them was my fav as well. Sigh.

Roan

PS
Is it a purple string on the rock? :D