Frustrating illness in C. schultzei

[Nikita]

I've been having trouble with a batch of c. schultzei. I got the adults at one of my LFSs early last year. One of the males (4m, 2f) got sick with what only seemed to fit an internal infection - reddish fins (not streaky) which were folded a bit, darker colour generally, listless and losing weight/condition. I treated the tank with Interpet's anti internal bacteria and it took a couple of weeks, but he did regain health.

Last autumn the group spawned, and I had over 300 fry from it. Shortly after that, the above male suddenly went sick again and died. The fry grew well to about 1/2" then I started losing them.

Since then, I've had waves of whatever this is - I only have 9 fish left from that spawning and am in the midst of another bout now. Not as bas before though. Each time it's the same - the affected fish go dark, fins redden and fold, weight is lost and they get listless. But, they still eat just fine.

During the last bout I asked for help elsewhere and someone had had success treating what appeared to be the same affliction with Protozin so I tried that; it did help somewhat although I lost the worst affected fish then (one in particular very quickly went down with pop-eye and severe dropsy, although she is the only one I've seen go that way).

I can't get a decent picture unfortunately but I can tell you that there is no spotting, growths etc, nothing indicative of ich/velvet/fungus. This time around a couple of the fish that have died have lost their tails but they didn't appear to have finrot - the tails just eroded and evenly too (from the join of the two lobes of the tail outwards).

Parameter wise, ammonia and nitrite are 0, nitrate is currently around 40ppm. That has been a problem - my tapwater comes in at 30ppm so it's been a battle to keep down but I am on top of it now.

I suspect this is something possibly genetic - in the tank with the remaining juveniles (now around 3/4-1" long) are two juvenile bristlenoses (added when I thought I'd finally gotten on top of the problem a couple of months ago), and they have always been in perfect health so this appears to be restricted to the cories. In the adults' tank there are other young bristlenoses and 7 cherry barbs and again, none have been affected - and when I lost the first adult male, they were in a different tank with different fish and same again, only that cory was affected. I have also lost another of the adult males, not long after the spawning that produced these fry happened. Very sudden, same symptoms. Interestingly, I noticed the other day that the healthiest of the remaining juvies look like they are females. I'm back to the Interpet treatment now as whenever I try to find answers, it all points to an internal infection. I can't get medicated food (none available locally and too expensive to ship over).

Does anyone have any ideas? I won't be saving eggs from the adults again although the remaining four are in excellent health, and the remaining juvies won't be going anywhere either. I have the space and filtration to accommodate any or all that survive and I don't want to potentially pass this problem on to anyone else so they will all be staying with me.

[Corycory]

I am really sorry about your corys. It's devastating, especially when you can't fix it and watch them drop one by one.

I am afraid I can't diagnose what they have but I'd like to ask have you checked the Ph, Kh and Gh of the water? Any changes? With 300 corys you can have the Kh get down to 0 pretty fast and pull the Ph down causing stress to the corys and in turn trigger diseases or death. It's just a thought.
Ammonia to nitrite conversion is very acidifying process and in a fry tank this can happen because of the high amounts of food and normally overload of fry despite of 0 readings for ammonia/nitrite.

It does sound like some sort of bacterial infection, possibly additional finrot because the initial disease was not eradicated, could be a combo of everything, including parasites. It's really impossible to tell. Hope the remaining make it and survive.

[Nikita]

Thanks for the reply. I haven't checked them, no - I didn't realise that could happen, but I've not tried to raise such a large batch before (successfully raised ~40 cories years ago with no problems at all).

I've lost another one since my post - his tail had started to go though so I was expecting it. The rest looks like they are improving again now, but I'll get the water tested asap.

[Corycory]

Hope the rest make it through.
It's a lot of corys. I'd do daily large water changes. Keep the tank clean of any decaying stuff, clean filters. It always helps.
Test the water, the Ph shouldn't be swinging and it's best to have some sort of Kh to prevent the Ph from dropping. My water is hard. I have a Kh of 8 but even 3-4 is enough with regular water changes to replace the used buffers.

I know you said your stats for ammonia, nitrite are fine. I would test a couple of hours after feeding, before water change...etc...to make sure it's not some sort of mini spikes. These are a lot of corys. You need superb filtration too. In a 60l tank I had to have two running filters to raise 40-ish corys and that's not even to full size, just enough to move half of them.

The reason I mention that it's still possible to have ammonia/nitrite spikes is because long time ago when I bought my first corys(still alive) I subjected them to an ammonia spike by accident although it was a fully cycled tank. For some reason thoroughly washing the sole filter caused a sudden spike. Symptoms were some of the corys tails and fins deteriorated over night!!! Obviously they weren't really swimming well around or just stood still.

Ammonia can eat through flesh pretty fast. I moved the corys immediately to another tank in order to sort the problem one and their fins regrew in about 2-3 weeks. They've been with me for about 4-5 years now.

[Brian2014]

Hi Nikita, sorry to hear about your losses it does sound to me like a internal infection if you can get your hands on it I would try Maracyn TWO by Mardel I have found it to be very effective it is a broad-spectrum antibiotic developed for use in the aquarium it is absorbed by the fish through the skin so gets to work very fast. When I had a out break in my pleco tanks I treated the tank with Interpet's anti internal bacteria like you then did and a dip teatment of Maracyn TWO and USNEA and I managed to save all the other plecos , touch wood I have had no sign of the problem again. Usnea is a herbal extract interesting article here http://www.aquarium-pond-answers.com/20 ... emedy.html was safe to use on my plecos and fish but I do not keep corys so I do not know how sensitive they are. As for the Maracyn two you might be able to find it on ebay or http://www.vitamingrocer.co.uk but last time I checked they had sold out very popular product. hope this might help in some way and good luck with the rest of your corys

[Nikita]

Thanks very much guys. There aren't a lot of cories now - down to 8 since that last one died, they are just coming up to an inch long.

I'll have a look at that treatment

[CoryfanAad]

Thanks very much guys. There aren't a lot of cories now - down to 8 since that last one died, they are just coming up to an inch long.

I'll have a look at that treatment

What are you feeding them Nikita?