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Corydoras going pale and dying - internal parasites?

rubadudbdub

Member
Joined
27 Oct 2015
Messages
138
Firstly sorry for the long post. I'm hoping some cory or fish heath enthusiasts will make it to the end and offer some advice. I have had an issue with my panda corydoras for a few months. I started with a small group of adults which then laid eggs in the tank and a steady trickle of fry have survived since May 2020 bringing the group up to about 12. The odd youngster (2 over 6 months) seemed to struggle, stayed rather thin and did not grow as well. Typically they then go very pale, look lethargic and disappear in the fairly densely planted tank. In the last month one of the young adults has done the same and then one of the original parents. Both of the latter had lost some of their whiskers, with the parent looking noticeably thinner. I moved these two into a bare tank with mature sponge filter and initially treated with methylene blue/malachite green, then an anti fluke/wormer (flubendazole 10mg/ml treats 50 litres). The young adult died, the older one is looking a little brighter, less lethargic and feeding better. Last Sunday was the 3rd weekly dose of flubendazole.

Rightly or wrongly, I'm leaning towards it being some kind of intestinal parasite. There is nothing visible externally, I rarely see the fish scratch, although they do from time to time.
Around 14 months ago I put a group of 6+5 pygmae corys in the same tank from TA aquaculture and Sweet Knowle, both of whom are good shops that quarantine. 2 pygmaes were similar to the pandas above, quite pale and slower than the rest. This pair also had peculiar behaviour, they were far bolder and would hang vertically completely still above the substrate. It reminded me of a parasitology lecture at uni where parasites would modify host behaviour to increase predation risk as part of their life cycle. I decided to treat the whole group but after 2 hours of chasing only caught the 2 pale slow fish, both of whom died. No problems with the rest of the pygmaes since.


Tank: juwel Rio 125, eheim pro2 external, water changes 50% every 3 weeks.
Substrate: 2/3 of the tank has a 2" substrate with lots of crypts/vallis nana with gravel over JBL aquabasis, 1/3 unipac samoa sand shallow covering ~ 1.5cm - its rarely got much in it when I clean it. There is some half buried redmoor root that the pygmaes live under, making catching them extremely difficult. I usually have a fairly thick covering of floating plants.
Fish: 8-9 pygmaes, 6 panda corys adult/young (I've moved some out now) with a 2-3 tiny fry, 8 rummy noses and a few aging endlers. Over the last few months I've been raising Nothobranchius and Fundulpanchax fry in a Ziss breeding box in the tank without noticeable losses. Also a colony of cherry shrimp and 3 large amanos.

If I'm honest I don't really know what I'm treating but the steady trickle of sick fish is making me wonder if I should uproot all the redmoor half buried in the substrate, trim the plants, catch the corys and treat them all even if those remaining look healthy for now. Parasite treatments seem not to be shrimp safe, otherwise i'd dose the tank. There was also ~7-8 months between the pale pygmae corys dying and the first panda fry looking pale and lethargic. So I accept there's a good chance the two issues are unrelated.

I associate lost cory whiskers with poor water quality. I have checked nitrite and its zero, although i could/should up water changes to fortnightly. The original spawning adults are still spawning this week, cory and fundulopanchax gardneri fry are happily growing, so my gut feeling is the water is OK. However, I did get caught out with some rich soft artemia feed from TA that a large group of cory fry (in another smaller tank set up with soil) hoovered up like sweets and caused a chronic low level of nitrite (lowest colour on the tetra kit) when I started chucking it in too liberally. This coincided with the extremely hot weather and I lost 20 ~2cm cory fry, lesson learnt, don't over feed young fish. Even if i assume this tank was also over fed last summer, it is months past that now and I still have an issue, despite the other fish seeming ok and new fry appearing.

I'm interested in people's thoughts. Does the story sound like an internal parasite problem, if so which are the treatments to go for and what would you do? What are the more common corydoras pathogens in people's experience, as common things are common? I have a new rio 240 that I've just set up that is maturing with some goldfish and the plan was to build up to large shoal (30-40) of pygmae corys along with the pandas I have currently. I am loath to seed a problem into a new tank, and have an opportunity to treat fish as i move them to the new tank. If I can decide whats wrong with them and what treatment to offer. Any advice or critique is very welcome. Thanks
 

Raws69

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5 Oct 2020
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196
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Essex
hi someone hopefully will jump in re the fish health, but 50% water changes every 3 weeks doesn’t sound enough And is likely to be affecting water conditions, are you using test strips? As these are notoriously unreliable. Maintenance schedule is recommended to be weekly 50%.
 

Simon Cole

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25 Dec 2018
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500
Location
Buckingham
Whisker damage, I have had solely due to sharp gravel.
I think you should consider your diet e.g. Grindal worms, blackworms, etc. before adding more "treatments".
Try listing things down - what you feed when, temperatures, CO2 levels.
Usually the right salts bath is enough to improve fish health if diet is not working, but I'll be interested to see whether helminths (parasitic worms) were the cause; you hear this rumour a lot in shops, but what about a dissection?
@Gill is a great person to ask, but lots of us keep these fish.
 

Conort2

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16 Feb 2018
Messages
539
Location
London
I’d try upping the water changes to 50 percent a week. Maybe even twice a week if you can for now. I’ve always associated barbel loss with poor water quality.

Cheers
 

Gill

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17 Mar 2008
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Location
SinFin Derby
@Gill is a great person to ask, but lots of us keep these fish.
I would agree that Upping the water changes to weekly at least should help.
Whisker loss, again I attribute that to the wrong gravel and poor water quality.
Which type of wormer are you using. At work we used this one every evening of fish delivery. Kusuri Discus & Tropical Fish Wormer Plus. And this was always the go to for parasites.
 

X3NiTH

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Joined
13 Apr 2014
Messages
1,165
@Gill the Kusuri stuff is also Flubendazole. If this is potential parasitism and an alternative is required then eSHa NDX is Levamisole based and should be the ‘Double Whammy’ to eradicate completely.
 

rubadudbdub

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Thread starter
Joined
27 Oct 2015
Messages
138
Thanks for your replies.
Sharp decor - its smooth fine gravel over the JBL, unipac samoa. Google doesnt bring up anyone saying its a problem. Redmoor root, a thin branch of which has disintegrated after 3 years in the tank. Dragon stone holds back the deeper section. I've not noted sharp bits, its mostly covered in anubias.
Feed - corydoras pellets and soft pellets from Ta aquaculture. I also coarsely (too fine makes a cloudy mess in the tank) crush up tropical flake with chlorella/spirulina flake and make a pea sized paste ball with a drop of water. This sinks better to the corys, adults and fry both like it and the tetras crowd around picking at it, also doesnt get caught in the dense mat of floating plants I usually have. Into this I add other fine stuff I've got around, fish science fine granules, astax fine granules. I alternate between pellets and flake balls. Frozen food, usually blood worm but I've got a few others once a week or so. Live grindal and tropical white worms once a week ish. Although the 'TWW' are smaller than the grindal so I'm not sure if these are actually white worms. This has dwindled recently as I need to redo cultures. Freeze dried blackworms infrequently as despite squeezing hard on the glass they almost always seem to float away, the corys do love them though. The odd squirt of BBS left over from feeding fry, the tetras nab this immediately. I've stopped feeding microworms as I was worried about pollution from them being so tiny and going everywhere. All these are not given concurrently for obvious reasons.
Dissection - I did try this with the the original sick pygmaes. The comic futility of it only dawned on me when the smallest blade I had was many times larger than the fish. I soldiered on without seeing anything obvious, then wondered what I hoped to see without a microsope. Is that a worm or some gizzards?
Temp 23 degrees, a hopefully happy medium between the needs of all inhabitants. I appreciate 22 is better for cory pandas.
CO2 - none, I've tried high tech and didn't get on with it.
Ferts - Duckweed index APF easy EI, although I've had issues with the floating plants not growing so well for 6 months or so, which from other threads on here I believe is an iron issue. The dosing bottle bottom has turned orange so its precipitating out. I've just bought and used one dose of sequestered iron to try.
Poor water quality / water changes WC are on an aspirational 2 weekly basis, with the reality being that I miss the odd one with busy home life and it becomes 3 weeks. It is an obvious thing to change. Perhaps erroneously I have associated breeding fish with acceptable water quality and not felt the need to stick to religious once a week or 2. Losing fish most certainly isn't acceptable. While WC have remained constant, losses are new (last 12 months), infrequent and now isolated to the pandas with everything else OK. I have in the past had walstad style soil tanks, no aquascapes but heavily planted with thick jungles of saggit/vallis/crypts with even less frequent WC. Until a couple of weeks ago there was a mat of floating plants so thick that the tank looked quite dark. An aphid population that was impossible to eradicate meant I resorted to binning the floaters and giving the tall plants a crew cut so nothing reached the surface for the buggers to grab onto. I could have been placing too much faith in the filtration offered by the plants, until recently its all seemed to work fine and breeding fish maybe offered false validation of this. I have twice accidentally left the eheim off after feeding live food. The first time it was off overnight, I did a water change and tested nitrite every day for just over a week and saw nothing change, so the plants are removing quite a lot of the nitrogen. WC are an easy thing to change and probably sensible given the recent loss of floating plants from the balance.
Testing - I use the tetra liquid tests. I find the dipsticks pointless. I am aware of the controversy. I believe the qualitative colour change from the bright yellow of no nitrite to pale orange at least provides some indication something is different or not, as it did with the fry grow out tank I over fed (went orange). The tank with the odd cory going skinny and pale is always bright yellow.
Treatment - its the flubendazole from NT labs, or rather the MA own brand version. I found the esha prazaquintel GDEX, if things carry on despite increased WC I'll look up the esha levamisole. I haven't tried salt baths.

As it currently stands the adult panda is still looking a little skinny and pale but brighter and more active. The other 'treated' one died, hardly a controlled trial. The rest of the breeding group in the main tank are as plump and active as they've ever been. A mindset change to 'this is optimal WC frequency' vs 'this seems OK so far' is sensible to eliminate this first.

Thanks for all your help. Any more thoughts gratefully received.
 
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