Can cory-toxic kill other fish?

[Sterbai22]

Two weeks ago I lost three corys and an angelfish all within 24hrs.
It started sunday night when I found a dead cory. Sad but well, they are all old, it can happen, I thought.
On monday lunch my husband found another one dead. I came home from work and found the third one also diseased. Now this was strange so I did some water tests, nothing odd except a small rise i pH (Unfortunately I only had test strips for pH since the drop test ran out. Nitrite, ammonium etc I had drip tests for). Tested three other tanks and the pH was normal, agaid in the affected tank and confirmed higher (usually 7,5 then almost .
While I did a water change, which was on monday afternoon, 8 days since the last one) one of my angelfish also turned in, just like that.

All the other fish were fine, except the diseased angel’s partner who got depressed and did not eat for almost two weeks and turned pale and he was also hiding a lot.
The other couple had no clue what was going on and layed eggs and looked happy.
The other day, the widower started to eat again and looked better and didn’t hide as much but still pale. But I thought he was out of danger. Well today I found him upside down. Nothing to be done. As I prepared to put him down he died on his own.

Now the question: can the corys have gotten stressed somehow and released toxic and killed my other fish? Seems so strange to loose three fish in that short time with good water and no visible sickness on any fish…

[Sterbai22]

Should say 8, not a sunglass smiley…

[bekateen]

Hi Sterbai22,

Everything we know about cory toxin is that it wouldn't behave that way. The toxin is a mixture of enzymes that create substances in the victim's body to cause pain, tissue damage and probably inflammation. Death occurs within minutes or maybe an hour. To work, the toxin has to be relatively concentrated. Since many people try to "purge" their corys before shipping by chasing them around in the tank, to pre-release the toxin (presumably leaving the toxin in the tank), and they do it without harming other tank inhabitants, this tells us the toxin is too dilute in the tank.

More than likely, something else is to blame for the deaths.

Sorry for your losses,
Eric

[Sterbai22]

Thanks for the answer. Yes it seems so strange but I had to ask since I came across the information on cory-toxic while googling for possible causes.

I have had theese corys for 1,5 yrs and I’m at least the third owner so I guess they were old but still wierd that all die at once. Maybe something else was off. Asked in another forum and they asked back if I had used any chemichals around the tank. Well we did clean the house that same weekend but only used a small amount of Jif in the water while mopping the floor. I also have birds and think they would have reacted if chemichals were an issue.

Is there anything else that corys can be especially sensitive for? Or angelfish for that matter?

[Shane]

Sterbai22,

Unfortunately, I am not sure that we will know what caused you to lose so many fish so quickly. If you ever encounter a similar situation here is what I suggest.

The minute you observe any odd behaviour or find a dead fish in what has been a healthy, stable tank:

1) Check that filters are operating normally and are clean and free of obstructions
2) Check tank temperature. Inspect heater for any signs of damage
3) Immediately perform a 50% water change with conditioned water similar in temperature to the aquarium
4) Observe fishes closely for the next 24 hours

The above four steps can be considered immediate "first aid." Testing the water is not helpful as the fish are telling you something is wrong no matter what the test say.

Only consider medications if your 24 hour observations lead you to identify a specific fungus, virus, or parasite. Many aquarists go straight to medications which often make things even worse as they can have unintended consequences on the fishes and/or aquarium. For example, the active ingredient in one "anti fungal" medication widely available is chlorine.

Sorry about your losses but hope the above will be useful to you in the future.

-Shane

[bekateen]

Is there anything else that corys can be especially sensitive for? Or angelfish for that matter?

Sterbai22,

Unfortunately, I am not sure that we will know what caused you to lose so many fish so quickly.

-Shane

Hi Sterbai22,

I agree with Shane on this one. Sometimes we can point to a singular condition or event that leads to mortality, but in many cases it's never clear. Clean, well aerated water is often the best remedy.

Good luck going forward,
Eric

[Sterbai22]

Thanks Shane. I will keep this in mind but I hope it doesn’t happen again

[Sterbai22]

Hi Sterbai22,

I agree with Shane on this one. Sometimes we can point to a singular condition or event that leads to mortality, but in many cases it's never clear. Clean, well aerated water is often the best remedy.

Good luck going forward,
Eric

Thanks. Yes I know sometimes it is just better to move forward. Hope this was a one time thing

[KamiWhit]

Hi,
I ran across this situation recently and thought I would share.
Black Friday our local PetSupermarket ran 50% off sale so I have 10 tanks so we went shopping.
I had 2 corydoras and was told that they do better in groups of 4 or more so I got 5 more albinos and 3 pandas.
I also got 8 female Bettas (for sorority) along with Molly's and platys and clown plecos. I was using several 20 gallon as a quarantine tanks and put all Bettas and corydoras in one tank and livebearers in another before putting in my 60 and 50 gallon tanks. Corydoras and Bettas were bagged separately from the store. Within an hour my first female died. I was watching very close as even though they were babies and actually stored together in the tank at the store, I was aware of possible aggression. One by one over 72 hour period all the Bettas died. Non of the Corydoras died. I did water checks and changes and called every store I knew of for advice. Took water samples in to the stores and everything was fine. They said the same thing as on here.... must be something in the water. PetSupermarket was wonderful and gave me full credit (unfortunately had to buy new fish at full price). After water changes I then purchased 6 dwarf gourami. These were much bigger fish and I could tell when something was wrong. After just being in the tank a few hours they started nose diving into the sides and bottom and acting erratic and then 4 of the six died over 72 hours. When I only had 2 gouramis left my husband said it has to be the Corydoras.... which is when I first found out about their toxin. Even though the 2 weeks of quarantine was not up, I put the Corys in the main tanks with the other 2 Corys. The remaining 2 gouramis lived and I replaced the 4 that died. Amazingly no one died after that! After 2 weeks I transferred the 6 gouramis to main tank. Now Jan 4, I find a gourami not acting right. I keep watching and up floats a dead Cory. I moved the gourami to a sick tank and he starts nose diving and laying on the bottom gasping for air like the gouramis did back around Black Friday. Looks suspicious. My husband and I love watching the Corys dart around the tank. He calls them "little assassin's". He may be right! I might have to move them to a live-bearer tank. The Corys don't seem to "kill" the live-bearers. FYI both Bettas and Gouramis are labyrinth fish (can breath air), which might make them more susceptible to the toxin. Anyone else have this happen to them?