The Whole Shebang

[Vale!]

It's interesting to hear that Corys and milky bagwater is really a thing. In which case I join P in wondering if it's caused by something excreted by the fish! That in itself seem reason enough to go for MW's activated carbon strategy (AC wouldn't have any other beneficial effect in context, I don't think). I've got a mammoth water-change lined up for tomorrow, so I'll do that and then run some carbon - I think I know in which section of my museum to look.

It's a few years since I was full-on South American but I have it in my head that only some species of Cory excrete toxins. Maybe I'm misremembering, or maybe knowledge has moved on since then. I wonder where @Vess is. I'll see if I can have a bit of a read-up on it in due course anyway.

The profusion of micro-life in the bag would have consumed dissolved oxygen.

I don't know whether they're wild-caught ; I'm guessing probably not. I've sent the supplier a link to my last post (he's acknowledged) so if-and-when he reaches this bit maybe he'd be able to say either way (via me).

Yes, GL - the tiny amount of bagwater that got into the tank must be so diluted now as to be insignificant (I think!) in terms of harmfulness. And Trichodina is a 'nasty' to fish. I'm not wholly convinced that what I saw is that - though something like it is certainly in the frame.

[Vale!]

I've found some useful papers - I'll digest a couple of them tomorrow and try to post the links.

[Martinspuddle]

The toxic problem, it is a defence. Corydoras are capable of releasing a poisonous mucus from the gills, pectoral fins and unfortunately can be their demise in transportation from stress. In the wild, is believed they release this toxin when stressed to warn off a potential threat or predator. In larger volumes of water to toxin is not so much of a problem, the problem comes of being transported in a small volume of water.

My late mother (she kept and bred Corydoras catfish for many years) come across this problem with her Corydoras and she tried a number of options to cure the problem I don't think she was ever successful. She said it didn't seem matter if they were wild caught or bred in captivity, once they release that toxin though stress in small enclosed space there is no come back I'm afraid.

The only suggestion I'm going to make you since the days that my mother kept them, is that you buy them direct from the dealer and you insist on using something like Stress coat or easylife fluid medium is added to the bag before you leave the store. Keep them in the dark and well insulated, I use a cool box with towels and a shorter journey home if possible.

[Vale!]

I've looked through a couple of papers this morning (links at end). Some highlights which may be of interest and/or relevance in context …

Researchers reference the 'cloudy bagwater' phenomenon seen by retailers and by keepers when Corydoras are transported.

Up to 2006 it was known that species "[in] at least nine" of twenty-one catfish families secreted toxins. It seems there had been few, or no, studies of Corydoras species specifically.

It had been seen that in catfish generally, toxic secretions come from : 'club cells' in the skin ; clumps of cells around the first pectoral fin ray ; and axillary glands (openings next to the pectoral fin) that occur in some of the fish. Such secretions from skin had been studied but little was known about those from axillary glands except that the toxic effects from skin secretions were presumed to be greater than those from axillary glands.

The secretions were presumed to be part of the fishes' defence mechanisms. It had been noted that there was a bactericidal effect - specifically on Vibrio fischeri but possibly more widely.

The two papers I've linked might be the first to look at Corydoras in particular in this context. Several C. species are referenced and all seem to possess axillary glands (that's not to say that all C. species have them, of course) and there's evidence that axillary glands contribute to the 'cloudy bagwater'.

One of the papers describes how six C. sterbai were bought from a retailer and transported back to a lab in 2.5 litres of water. They discharged substances that turned the water cloudy. 250mls of this water was freeze-dried and revealed 73.5mg of 'raw toxin'. So by calculation : 735mg raw toxin in total in that bag. 'My' bag had double that number of fish, so it seems likely that there could have been up to 1.5 grams of toxin in the bag (assuming that C duplicareus behave in the same way as sterbai).


Link 1 : https://www.researchgate.net/publicatio ... luriformes

Link 2 : https://www.researchgate.net/publicatio ... luriformes

[fr499y]

interesting bit of research.

[plankton]

I don't think many people realise that they do excrete toxins.......that's why I ask for them to be rebagged after catching before I transport them, and add Melafix to the bag and the tank during transfer.

[Fishtales]

Fortunately I haven't suffered any fatalities so far with my Cory Aeneus through the post. Reading this (and I am not going to pretend I understand the linked articles!) I will definitely speak to the supplier before I get more (different type) for my 125lt tank. Check if he is taking the precautions @plankton mentions. Very interesting, and pretty sad as well.

[Vale!]

Since my last post I've almost certainly cleared both silk plants and filter foam from any blame. I've done a >80% water-change but haven't yet run carbon because something else has occurred to me which I need to clear up before I introduce more fish.

The facts that the pencilfish fell overnight and that the blackworms haven't behaved in the way I'd expect them to (though they're still alive) are worrying me greatly. The only thing that I've used in the project which is unusual is the black glass.

When I first had the idea for this, and before buying, I contacted the supplier(in Bristol) with an enquiry about the integrity of the dye(s) in water. The reply I got (16/06/19) was :

"the colourant in the glass we sill [sic] is part of the glass itself, so will not wash out or fade with UV light / water exposure. It is coloured all the way through the sheet."

What I did not do when it arrived was test the glass against living things. I suppose it's a bit of a long shot but it's a definite avenue to explore.

The glass is made in Mexico (I think) so I've contacted the supplier to see if he can tell me, or help me trace, the manufacturer's name. If I can discover what exactly makes the glass black, I can maybe chase up MSDS info for that/those chemicals.

Meantime, I've set up a test. Two pint glasses filled with bathwater, each with some extra food and a number of Daphnia. One glass has a couple of pieces of the black glass in it :



I'll report back on progress. Of course if this were to turn out to be a valid suspicion it would have implications not only for Sheba 4 but for Shebas 1-3 also. I'll cross that bridge if-and-when I come to it!

[plankton]

Hold on, if the corys were problematic when they arrived, how can it be glass that's caused the problem?
Or are you just eliminating possible future problems?
Or am I confused as usual?

[Vale!]

It's because a small group of pencilfish, which I introduced at the same time as the Corys, perished overnight.

I'm thinking : either a pathogen transferred astonishingly quickly from Corys to pencilfish ; or there's something toxic in the tank.