Cories are dying

The reason I think it's fin rot is that they have white on the edges of their tails and because you have a lot of aeration which can help with filtration in a way. One of the causes of fin rot is filtration is too strong that's why I say this.

Another question do some of the bigger fish nip at the smaller fish? If so it is most likely fin rot.

This is a good YouTuber that helps tell you more about fin rot. https/www.youtube.com/watch?v=wICf_0o6ys4

fisman said:

Can you send a picture? It might be too much oxygen in the tank.

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you can't have too much oxygen in the tank

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Pictures of the fish?

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?

What sort of filter is on the tank?
How often and how do you clean the filter?
What is the ammonia, nitrite, nitrate and pH of the tank water?

To treat white spot with heat, you need to raise the water temperature to 30C (86F) and keep it there for 2 weeks or at least 1 week after all the white spots have gone from the fish.

Did you use a chemical to treat the fish for white spot?
If yes, what chemical?

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If the fish have a cream/ white film over their body or fins, it is excess mucous caused by something in the water irritating the fish.

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.

Hey sorry, I went to bed. Everyone’s fins look fine. The dead ones I’m pulling out are fine except the fire mouth likes to eat their faces. I had one of the loaches die awhile back from fin rot so it was one of the first things I looked for.
The fire mouth chases the largest loach around the tank but I’ve not seen him go after any of the littler fish; that’s one of the reasons I like them. They can be slightly aggressive but for the most part it’s a happy tank.

Colin_T said:

you can't have too much oxygen in the tank

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Pictures of the fish?

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?

What sort of filter is on the tank?
How often and how do you clean the filter?
What is the ammonia, nitrite, nitrate and pH of the tank water?

To treat white spot with heat, you need to raise the water temperature to 30C (86F) and keep it there for 2 weeks or at least 1 week after all the white spots have gone from the fish.

Did you use a chemical to treat the fish for white spot?
If yes, what chemical?

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If the fish have a cream/ white film over their body or fins, it is excess mucous caused by something in the water irritating the fish.

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.

Click to expand...

I do water changes about every 2 months. I did one about a month ago and i did 50% cause I was overdue by a month in getting it done. When I do those everything gets cleaned, gravel, glass, scrub down excess algae. I do the filter when it tells me to, whenever it turns red. I did a deeper cleaning on it when I did the last water change because it had some crazy algae growth that I didn’t like. It’s been fine since then.

All 4 of the water tests were perfect last night when I did them.

I did up it to 86 when I was dealing with the ich, and did salt mostly because the loaches can’t handle the medicines. I did use them but in a greatly reduced capacity. I’ve been scared to lower the temp cause it’s such a pain with loaches to beat and everyone has been happy in there for months.

I don’t see any white spots of film on any of the fish. The rainbows have specs of silver that sometimes look white but aren’t, and their tails have a white line at the bottom of them normally.

Water changes should be done more often than every two months....most of us do them weekly

Colin will sort out issues, but a couple of obvious things stand out that I'll mention.

In post 1 you say the cories keep surfacing...this is normal Corydoras behaviour. All species in the genus will periodically and fairly regularly swim quickly to the surface for a gulp of air. The fish swallows the air and blood vessels in the hind gut extract oxygen from the air; it is then expelled through the vent the next time the fish breaks the surface for another gulp of air. This adaptation is believed to have evolved so that the fish can survive in poorly-oxygenated water such as drying pools during the dry season. It is however essential to the fish's well-being that it regularly swallows air. However, if the frequency of these surface breaches increases significantly, it means something is wrong. It's not clear if this surface breaching has been occurring, or if it only started with the increase in temperature.

When you say all tests are perfect, please always give us the test numbers if you have them. Different people have different ideas about what is or isn't good when it comes to test results, and we need to know specifics.

The high temperature will burn the cories out, but it is OK to have the higher temp specifically to treat ich or something. Just make sure the temperature is lower when this is finished. Or remove the cories then if for some reason you retain the higher temperature.

Water changes must be weekly, at minimum. And substantial, all else being equal. The article pinned at the head of the Tropical Discussion forum explains why this is so important.

Corydors and loaches should never be together. I am frankly surprised the clown loaches have (I assume) tolerated these cories to date, but then maybe they haven't, if something is nipping cory tails it is likely the loaches. Moving forward, it would be best for both species to remove the cories.

You can't really do too many water changes so I would start doing your water changes more often. I would do 30-gallon water changes on that weekly. The more water changes the better the water quality.

seems like you are running the heater at about 28/29 phew I’m sweating just thinking of the corys.That’s far ?
Corydoras need clean,well oxygenated water.Monthly water changes don’t cut it,make it 30% twice weekly.
Turn the temperature down one degree each day over the next 6/7 days.
22 is a good temperature for corys,a bit low for everything else,but they can handle it,only their metabolism will slow.

Sorry, seems like this baby is coming soon so I’ll have to get back to this next week.
The water levels,
pH - 6.8
Ammonia - 0
Nitrite - 0
Nitrate - <5

I can do water changes more often. I can also get the temp back down.

something one of you said got me thinking, we’ve had cories and loaches in the same tank for at least 12 years and never saw an issue. BUT there have always been places to hide. When the fire mouth tore out the latest round of plants, it was most of where the cories stayed exposing them. And they don’t like leaving that corner except to scavenge. It seems to me this issue started about the same time he ripped all that up. I will get more plants for the remaining 2 sooner then I was planning and hopefully that will solve the issue for the immediate moment.

thank you to everyone for your help and input. If there are any others, I will take it all in and apply it. It will however be a few more days before I can do much about it now.

The fish in the pictures look fine and don't appear to have a disease. They could be dying for a number of reasons,
Territorial issues with other bottom dwellers,
The firemouth/s might be breeding or are getting angry over territory,
There could be damage to the gills from the white spot parasites.
There could be a build up of microscopic organisms in the water that are affecting them,
There might be chemicals/ hormones that have built up in the water and are stressing the fish.
It might be temperature or medication/ chemicals

If possible try to do a water change and gravel clean every 1-2 weeks, weekly is preferable so you get into a routine. Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

Filters should be cleaned at least once a month. Wash the filter media/ materials in a bucket of tank water and re-use the media. Tip the bucket of dirty water on the lawn.

Do daily water changes and gravel cleans for a week and see how the fish go. If more die, post pictures of them.

hey, did you find out what was the cause of the deaths, as we lost one of ours recently, and my sister is convinced that it was because of too much oxygen? we do follow this one blogger and the guide helped us cure hyperoxygenation and our cories are healthy for now. but I am curious if there is something else I should be careful of.

john-Alce said:

hey, did you find out what was the cause of the deaths, as we lost one of ours recently, and my sister is convinced that it was because of too much oxygen? we do follow this one blogger and the guide helped us cure hyperoxygenation and our cories are healthy for now. but I am curious if there is something else I should be careful of.

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LOL....from that link:

To reduce the hyperoxygenation in your aquarium, you must try the following solutions.

1. Add more plants to your tank. Plants will consume excess oxygen leaving a higher concentration of CO2 in the water, which is necessary for fish.

Plants consume CO2 and give off O2, not the other way around....

john-Alce said:

hey, did you find out what was the cause of the deaths, as we lost one of ours recently, and my sister is convinced that it was because of too much oxygen? we do follow this one blogger and the guide helped us cure hyperoxygenation and our cories are healthy for now. but I am curious if there is something else I should be careful of.

Click to expand...

So I had forgotten about this! I lowered the temps and added a lot more plant life again. Plus about 1-3 weeks after this post I broken down the whole tank so I could move it. I haven’t lost any since posting this.

I made sure I got enough plant life for the firemouths to eat while allowing some to get some good rooting going. So far so good. I think the firemouths were being territorial. We had a lot going on with renovations that I think wasn’t helping.