Two dead Julii Cory Catfish

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Aquarium Advice Newbie
Dec 5, 2022
After overcoming a huge fish wipeout of my 30 gallon tank and resetting I bought some julii corys to help keep the algea under control. Other than those two I have 1 emerald cory cat, 3 adult yellow orange tail guppies, 1 yellow black adult guppy, 20 baby yellow orange tail guppy, 3 cardinal tetras. How ever a Julii cory cat died yesterday to an unknown cause and the only thing I noticed as a bit of popeye that came up out of no where. And today the other julii cory cat died also to an unkown cause. there were no markings, color change, weird behavior, growth, or any signs of illnesses. All the other fish aren't showing any signs of being sick either. Any ideas on what might have happened?
Please take a read through the "unhealthy fish" sticky and answer the questions as thoroughly as you are able.

Corys dont eat algae. They are bottom feeders, often called clean up. They will eat left over food that gets missed by other fish and settles onto the substrate. They might try and eat algae if they are starving, or eat bits of algae wafer, but otherwise arent going to do much to keep a tank clear of algae.

Corys are also social fish, they do better in groups of the same species. 6 fish is often cited as the number of fish for them to feel comfortable. How many of julii's did you get? Im also looking at your loan emeral cory and the same can be said for your cardinal tetras. Tetras are also social fish, more so than corys.
I keep my little Cory albino cats in a small group of 6. They hang out together in a 55 G of peaceful fish.

I have experienced rapid death from a few fish bought from local large chain stores. They died the next day or a few days later. These fish appeared active & healthy at the shop & were added to good tanks: ideal water chemistry etc.

Multiple big box pet store employees told me the fish arrive in water tinted from sedatives & overcrowded. Last week I pointed dead fish out to a Petsmart employee. She said she had been picking dead fish out of their latest shipment multiple times a day. I’ve had much better luck at the smaller fish pet store, but even there 2 dozen rosy minnows began dying the day I brought them home and the calico fantail goldfish purchased the time died a few days later. The fantail went into a healthy 125 G tank with other goldies.

So I think you bought unhealthy fish that would not have lasted long In anyone’s tank. I’m so sorry. I know firsthand how disheartening this is.
We need pictures of the dead fish and any remaining catfish. Also a picture showing the entire tank.

Test the water for ammonia, nitrite, nitrate and pH. Post the results in numbers here.

What are the tank dimensions (length x width x height)?
How long has the tank been set up?

How long have you had the fish for?
Did you add anything in the 2 weeks before this started?

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?

What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).
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