Cory Died - Why?

JKunner · May 21, 2021

Hello!
I’m relatively new to fishkeeping and new to this forum. I’d like to find out why my Peppered Cory died today!

I’ve had 2 Corys for around a month now and never had any issues, until this last week where they’ve stopped eating as much and have hidden away under some decor (the hiding wasn’t uncommon during the day). I came down to find one of the Corys had died overnight with some redness around the belly (pic attached).

Immediately did a water test but Ammonia, Nitrite and Nitrate are all 0. They tended to eat Tetra Micro Granules and King British Catfish pellets. The other Cory doesn’t have any redness and isn’t showing other symptoms of dying.

Is the death due to a disease or from under-eating? I’d like to know if the rest of my fish are in danger. I have a 120L tank with: 1 platy, 6 cherry barbs, 1 Cory and 3 Oticinclus.

Thanks!

Fishfinder1973 · May 21, 2021

A lot of the time it can be a case of a weak fish to begin with.It’s always a good idea to buy corys in 3s,as after some experience with them,ive found that there’s usually one that will be weaker than the other two.
As long as your parameters are ok then I wouldn’t worry about the other fish in the tank.

Colin_T · May 21, 2021

looks like a bacterial infection (red patch on the belly).

how long has the tank been set up for?
how often do you do water changes and how much do you change?
do you gravel clean the substrate when you do a water change?
do you dechlorinate the new water before adding it to the tank?

what sort of filter is on the tank?
how often and how do you clean the filter?

----------------------
If a fish dies in the tank, do the following.
Wipe the inside of the glass down with a clean fish sponge.

Do a 75% water change and gravel clean the substrate every day for a week. The water changes and gravel cleaning will reduce the number of disease organisms in the water and provide a cleaner environment for the fish to recover in.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

Clean the filter if it hasn't been done in the last 2 weeks. However, if the filter is less than 6 weeks old, do not clean it. Wash the filter materials/ media in a bucket of tank water and re-use them. Tip the bucket of dirty water on the garden/ lawn. Cleaning the filter means less gunk and cleaner water with fewer pathogens.

Increase surface turbulence/ aeration to maximise the dissolved oxygen in the water.

Sgooosh · May 21, 2021

2 cories is too small of a number, get a bigger tank and upgrade to 6. i have 10....
anwyay, thats all i have to say though

DoubleDutch · May 21, 2021

Colin_T said:
looks like a bacterial infection (red patch on the belly).

how long has the tank been set up for?
how often do you do water changes and how much do you change?
do you gravel clean the substrate when you do a water change?
do you dechlorinate the new water before adding it to the tank?

what sort of filter is on the tank?
how often and how do you clean the filter?

----------------------
If a fish dies in the tank, do the following.
Wipe the inside of the glass down with a clean fish sponge.

Do a 75% water change and gravel clean the substrate every day for a week. The water changes and gravel cleaning will reduce the number of disease organisms in the water and provide a cleaner environment for the fish to recover in.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

Clean the filter if it hasn't been done in the last 2 weeks. However, if the filter is less than 6 weeks old, do not clean it. Wash the filter materials/ media in a bucket of tank water and re-use them. Tip the bucket of dirty water on the garden/ lawn. Cleaning the filter means less gunk and cleaner water with fewer pathogens.

Increase surface turbulence/ aeration to maximise the dissolved oxygen in the water.

Agree with the diagnose bacterial infection.

Naughts · May 21, 2021

Cories need a soft sand substrate. If you use gravel it traps debris and increases the risk of infection to the fish's barbels and underside. If the gravel is sharp it will cause abrasions that can then harbour infections. Finally, cories filter sand through their gills to find food and will become stressed if they are prevented from doing so.

Sgooosh · May 21, 2021

Naughts said:
Cories need a soft sand substrate. If you use gravel it traps debris and increases the risk of infection to the fish's barbels and underside. If the gravel is sharp it will cause abrasions that can then harbour infections. Finally, cories filter sand through their gills to find food and will become stressed if they are prevented from doing so.

my cories just eat the sand, swish it around their mouth and spit it out

JKunner · May 26, 2021

Thanks for the responses All!

coriesinhawaii · May 27, 2021

Naughts said:
Cories need a soft sand substrate. If you use gravel it traps debris and increases the risk of infection to the fish's barbels and underside. If the gravel is sharp it will cause abrasions that can then harbour infections. Finally, cories filter sand through their gills to find food and will become stressed if they are prevented from doing so.

I know it’s not a popular opinion but cories are fine on small pea-sized gravel so long as it is smooth and vacuumed frequently. I mention this because cories are often not the only species in the tank so I think it’s helpful for people to understand that a sand substrate is not an absolute requirement in order to add cories to a tank. They would probably prefer a sand substrate though if given the choice.

Naughts · May 27, 2021

coriesinhawaii said:
I know it’s not a popular opinion but cories are fine on small pea-sized gravel so long as it is smooth and vacuumed frequently. I mention this because cories are often not the only species in the tank so I think it’s helpful for people to understand that a sand substrate is not an absolute requirement in order to add cories to a tank. They would probably prefer a sand substrate though if given the choice.

Sand is an absolute requirement for keeping cories. Not doing so denies them the opportunity of their natural feeding habit which is to filter food from the sand through their gills.

coriesinhawaii · May 27, 2021

In your opinion

Naughts · May 28, 2021

And Byron's.
And Ian Fuller's...
Play sand is the cheapest substrate and widely available. There aren't any fish that cannot live in a tank with sand. Plants grow well in sand. Follow the science.

Fishfinder1973 · May 28, 2021

When I first began with fish keeping,I only had gravel in the tank and my corys were ok with gravel.
My next tank,and I opted to go with 50/50 gravel and sand substrate.The back end has gravel,and that’s where the plants are,with sand along the front.I moved the fish into the new tank and noticed how the corys much preferred to eat from the sand substrate,burying their heads deep into it,and in doing so I noticed how much longer their barbules grew.
Corys can live ok with gravel,and I will argue that,but we won’t see their full potential.

coriesinhawaii · May 28, 2021

Naughts said:
And Byron's.
And Ian Fuller's...
Play sand is the cheapest substrate and widely available. There aren't any fish that cannot live in a tank with sand. Plants grow well in sand. Follow the science.

I follow my own experience over other people’s opinions or “science”

Madisonkeug · May 28, 2021

Naughts said:
And Byron's.
And Ian Fuller's...
Play sand is the cheapest substrate and widely available. There aren't any fish that cannot live in a tank with sand. Plants grow well in sand. Follow the science.

I’ve seen people use aqua soil etc and they work fine with them since it’s not jagged and they can still eat properly as well

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