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Gradually losing my pygmy corydoras

K

Katharine

Member
Joined
4 Oct 2023
Messages
132
Location
London
Tank - My first adventure into aquascaping - Aquael 125L Walstad

Tank:
125 litre
Filter: aquael pat mini
pH: 7.5
dGH: 10
dGH: 8
Temperature: 23⁰C
Ferts: EDTA iron & Epsom salt
Ammonia: 0
Nitrite: 0
Nitrate: 0

Inhabitants:
15 celestial pearl danios
12 otocinclus macrospilus
2 honey gourami
10 (down from 12) pygmy corydoras - added in last two weeks
5 black panther snails
1 nerite snail
~7 red cherry shrimp

Food:
  • NTLabs micro crumb (1 pinch daily)
  • Hikari sinking wafers (3 daily, up from 1)
  • Hikari mini algae wafers (3 daily, up from 1)
  • Repashy soilent green (small cube occasionally)
  • Mulberry leaf (1/2 a leaf sporadically)
  • Presoaked decapsulated Artemia (started adding today)

They become lethargic and hide on the gravel, often lying on their side, and occasionally swimming around a little. I've lost two so far but a third isn't looking good.

Their barbels and fins look healthy.

I've been gradually ramping up the number of wafers as they're always gone by the next day. Unfortunately all the fish are fans of the wafers, including the otos, so I'm not sure how well the corys are eating. All the other fish seem healthy.

I believe they're tank bred and are still juveniles (maybe 1cm long).

Possibilities:
  • Starvation - possible? I'm planning to start feeding the algae wafers spread around the tank, and decapsulated Artemis at night
  • Bacterial/virus - ???
  • Parasite - ???
  • Fungus - ???
  • Stress - seems unlikely?
  • Low oxygen - seems unlikely but I've got my filter on max with bubbles now to see if that helps

The one next to the bowl on the right is the one which is sick, you can see it looks much darker too:
PXL_20240202_192223916.jpg
 
What strikes me is that Cory has turned black - or am I miss-seeing that?!
 
Hello again - also, is this one or another fish? (On its side on the right).

Screenshot 2024-02-03 at 21.22.20.png
 
Hello! Sorry my notifications stopped working so I didn't think anyone had replied.

Yes they do seem to have turned very dark, it's very odd as when I've googled it people only really talk about corys going pale when they're sick. It's possible the colour is to do with them being smaller, or hiding in the dark and changing colour to match their surroundings?

And yes that is another fish - I made the call to euthanise it over the weekend so I'm now down to 9.

I'm currently trying feeding them more heavily to see if that helps as the sick ones do seem thinner. I'm splitting up the wafers and feeding at night, and feeding them lots of soaked decapsulated artemia.
 
I am really more of a Corydoras breeder than a planted tank guy, I keep about sixty species.
Generally the first suspect with sick Corydoras is bacterial, it may not show outwardly but be internal.
You need to look at the general health of the tank and the substrate, it looks to me to be quite dirty, feeding with extra food can compound the problem, under these conditions you can quite quickly develop a problem.
Try to clean up as much a possible and treat for bacterial issues.
 
Hi all,
Katharine said:
Starvation - possible? I'm planning to start feeding the algae wafers spread around the tank, and decapsulated Artemis at night
Click to expand...
I'm sorry for your losses, for <"whatever reason"> it isn't uncommon with Corydoras pygmaeus.

We don't exactly know why, personally I think feeding them a small <"live food item"> really helps, and that they also seem to benefit from <"some structural leaf litter">.

You are more than welcome to an established <"Micro (or Banana) Worm culture">, PM me if you want one.

cheers Darrel
 
Gerald Buswell said:
I am really more of a Corydoras breeder than a planted tank guy, I keep about sixty species.
Generally the first suspect with sick Corydoras is bacterial, it may not show outwardly but be internal.
You need to look at the general health of the tank and the substrate, it looks to me to be quite dirty, feeding with extra food can compound the problem, under these conditions you can quite quickly develop a problem.
Try to clean up as much a possible and treat for bacterial issues.
Click to expand...
Thanks very much for taking the time to reply!

I was under the impression mulm is generally good in a planted tank as it acts as a fertilizer - I guess like many things it has pros and cons? In any case I've done a water change this morning and removed as much mulm as I can.

The corys were unsettled by the water change and 8 swam round the tank together - I know this is a sign of stress but was reassuring to see them behaving normally. The ninth was resting on a leaf.

I'll be careful not to go too overboard on the feeding - maybe just focus on feeding them at night and distributing the food so they don't have to compete with the otos so much. To be clear the wafers are always gone by the next day so we're not talking lots of food building up in the tank levels of overfeeding.

What treatment/dose would you recommend?
 
dw1305 said:
Hi all,

I'm sorry for your losses, for <"whatever reason"> it isn't uncommon with Corydoras pygmaeus.

We don't exactly know why, personally I think feeding them a small <"live food item"> really helps, and that they also seem to benefit from <"some structural leaf litter">.
Click to expand...
Thank you. I've been adding mulberry leaves for the otos and snails, good to know they might be beneficial to the corys too. Though leaf litter seems pretty adjacent to mulm?
dw1305 said:
You are more than welcome to an established <"Micro (or Banana) Worm culture">, PM me if you want one.

cheers Darrel
Click to expand...
That's very kind, I'll let you know if I do. 🙂
 
Andy Pierce said:
You probably know this, but epsom salt is not fertiliser, it is MgSO4. For fertiliser you need a source of nitrogen, phosphorus and potassium (NPK).
Click to expand...
Yes it's a low tech tank but I'm trialling adding magnesium and iron in case there are deficiencies. Just included in the post for completeness in case they were causing an issue.
 
Hi Katherine.
Katharine said:
I was under the impression mulm is generally good in a planted tank as it acts as a fertilizer - I guess like many things it has pros and cons? In any case I've done a water change this morning and removed as much mulm as I can.
Click to expand...
I would support @Gerald Buswell in this comment. I would definitely remove as much mulm as possible. The fact that the Cory's are predominately bottom feeders here may be the clue.
Katharine said:
The corys were unsettled by the water change and 8 swam round the tank together - I know this is a sign of stress but was reassuring to see them behaving normally. The ninth was resting on a leaf.
Click to expand...
Water changes can cause stress to inhabitants as they can be disruptive, but water changes themselves (for fish) should not cause any health issues IF the rest of the tank is stable and healthy.
Katharine said:
I'll be careful not to go too overboard on the feeding - maybe just focus on feeding them at night and distributing the food so they don't have to compete with the otos so much. To be clear the wafers are always gone by the next day so we're not talking lots of food building up in the tank levels of overfeeding.
Click to expand...
Your challenge here is that you need to feed the bottom feeders before the swimmers get the food! However, fish are generally greedy, in my opinion, and if you leave a tonne of food around, they will do their best to eat it. i.e. just because there is nothing left in the morning does not mean the fish have had the correct amount of food. You are looking at 1-2% of body weight for adults and 2-5% for juveniles. If you have 6 young Cory's then you are only looking only between 0.2 and 0.3 grams of food for the whole lot.
 
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Katharine said:
What treatment/dose would you recommend
Click to expand...
I tend to use salt or Seachem products, not really sure what is available to you, salt will not work with plants, perhaps others can recommend a good bacterial treatment available in the UK. I do know Ian Fuller likes to use Melafix an API product, which is a natural melaleuca or tea tree oil based product.
 
Katharine said:
Tank:
125 litre
Filter: aquael pat mini

Inhabitants:
15 celestial pearl danios
12 otocinclus macrospilus
2 honey gourami
10 (down from 12) pygmy corydoras - added in last two weeks
5 black panther snails
1 nerite snail
~7 red cherry shrimp
Click to expand...
Also (as we are advising Katherine on the next step of treatment at this point in the thread), could I point out the above? i.e. 125L aquarium with the stated inhabitants running on an Aquael Pat Mini.

Does anyone else have any concerns over the filtration capacity here?
 
Hi all,
Katharine said:
Though leaf litter seems pretty adjacent to mulm?
Click to expand...
I'm guessing that not all mulmy matter is the same. The late Bob Marklew was <"definitely the best fish-keeper I've ever met">, and he had tanks with a certain amount of mulm in them.

Have a look at what Colin Dunlop has to say <"All the leaves are brown… — Seriously Fish">. I've never met Colin, but we've <"corresponded a bit">.

I'm not claiming to <"be a great fish keeper">, in fact <"quite the opposite">, but I've kept <"Corydoras pygmaeus"> and/or <"C. hastatus"> for the last fifteen years and they have <"done all right for me">*, on a diet of benign neglect.

* Hubris and I've probably cursed them now and they will all die.

cheers Darrel
 
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Hi @Katharine Sorry about the loss. Since you only had them for 2 weeks, I'd say they probably carried the disease from the store where you got them or they got stressed out from introduction in their new home - for instance if the water they came from varies wildly from your tank water - this alone may not be a problem if the fish is otherwise healthy but could weaken their immune system enough to make the disease they carry lethal.

@Katharine, I wonder how those cherry shrimps and Oto's are doing, are you loosing any of those?

Cheers,
Michael
 
Bradders said:
Does anyone else have any concerns over the filtration capacity here?
Click to expand...
It's a decently planted tank judging from this Journal entry ... but yes, I would be worried about lack of nutrient distribution / flow and oxygenation with such a low turnover you get from just one Pat Mini vs. the tank size and density of the plant mass. The Cory's are bottom dwellers and I can't help suspecting they may be exposed to low oxygen levels and possibly toxins from decomposing waste,

Cheers,
Michael
 
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It seems a general rule with the smaller corys that deaths can occur in the first 1-2 months. I had the same with habrosus. Just take the advice here and don't feel too bad.
 
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