My Corydoras are slowly dying

Ellabee said:

Hi. A couple of suggestions that should help. First of all, I think you are doing far too many water changes. Corydoras are very sensitive to “water that’s too clean”. And any temperature change, even a couple of degrees.. can cause severe stress and parasites. And your ARE supposed to rinse all filter media.. just rotate them. Don’t rinse them all at the same time. Do one type of media one week.. rinse another the next week. Also corys need food to eat. They really aren’t big on algae control. I can tell you right now, the dwarf Corydoras can’t handle chemicals or constant water changes. Personally, I don’t use chemical solutions intended for the plants. My plants thrive just from enough light. I’m the type of person that uses all natural treatment. Whenever I add a new fish or I see the first sign of any kind of issue,
MICROBE LIFT HERBTANA
Keeps immune system boosted. Follow instructions on label. A pinch of salt here and there.. as long as the fish aren’t scaleless, or sensitive to it. I think if you hold off on all of those water changes, keep the temperature stable at all times, cut back on the chemicals unless the levels are somewhere in a danger zone. My corys are spoiled and get a variety of nutrition. Best substrate for corys —Carib Sea Moonlight Sand. It’s very fine and soft. If you get a severe problem in your tank go ahead and get some methylene blue, follow instructions and make a dip.

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Colin_T said:

This is why you should always quarantine any new fish, plants, shrimp or snails for at least 2 (preferably 4) weeks before adding them to an established aquarium.

Fish spinning in circles is caused by a bacterial or protozoan infection in the brain. It regularly occurs in tanks with lots of rotting matter (gunk) in the filter and or substrate, and in tanks that don't get enough water changes.

The fact this happened 24 hours after adding the fish to your tank suggests the fish were sick before you got them, and they have introduced a protozoan infection into the tank.

The catfish with the damaged dorsal fin looks like it is being eaten by an external protozoan infection too.

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I would clean the filter (including the Purigen and Seachem Matrix) and any exposed areas of gravel (with a gravel cleaner). Do a massive water change and then add some salt.

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SALT
You can add rock salt (often sold as aquarium salt) or swimming pool salt to the aquarium at the dose rate of 2 heaped tablespoon per 20 litres of water.

If you only have livebearers (guppies, platies, swordtails, mollies), goldfish or rainbowfish in the tank you can double that dose rate, so you would add 4 heaped tablespoons per 20 litres.

Keep the salt level like this for at least 2 weeks but no longer than 4 weeks otherwise kidney damage can occur. Kidney damage is more likely to occur in fish from soft water (tetras, Corydoras, angelfish, Bettas & gouramis, loaches) that are exposed to high levels of salt for an extended period of time, and is not an issue with livebearers, rainbowfish or other salt tolerant species.

The salt will not affect the beneficial filter bacteria but the higher dose rate (4 heaped tablespoons per 20 litres) will affect some plants and some snails. The lower dose rate (2 heaped tablespoons per 20 litres) will not affect fish, plants, shrimp or snails.

After you use salt and the fish have recovered, you do a 10% water change each day for a week using only fresh water that has been dechlorinated. Then do a 20% water change each day for a week. Then you can do bigger water changes after that. This dilutes the salt out of the tank slowly so it doesn't harm the fish.

If you do water changes while using salt, you need to treat the new water with salt before adding it to the tank. This will keep the salt level stable in the tank and minimise stress on the fish.

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You can try leaving the lights on for an extra 1 or 2 hours each day to encourage algae for the Otocinclus and suckermouth catfish. Alternatively, you can grow algae on rocks or ornaments outside and bring them in each week for the fish to graze on.

Get a large plastic storage container and put it outside in the sun. Fill it with dechlorinated tap water and add 1 level tablespoon of lawn/ garden fertiliser for every 20 litres of water. Mix it up and then add some smooth river rocks or ornaments. Leave the rocks/ ornaments in the water until they get covered in green algae, then move them into the aquarium for the fish to graze on.

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The pH and GH are a bit low for guppies and Endlers but is fine for the other fishes. Guppies do best in water with a pH above 7.0 and a GH above 200ppm.

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Colin_T said:

If you have some Waterlife Myxazin, start treating the tank with that now.

Remove carbon from the filter.
Increase aeration.
Wipe the inside of the glass down.
Clean the filter if it hasn't been done in the last 2 weeks.
Do a big water change and complete gravel clean before treating (assuming you didn't do one the other day).

You can use salt and Myxazin together.

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N_F_S said:

Today, one more corydora dying. This time catch them before die, to be easier to spot external symptoms before start decomposition and also to try to quarentine him.

Can you understand the issue with this photos?

I also read about columnaris, and see some times symptoms are white zones, some times red gills. Do you think can be columnaris?

I’m avoiding to rely on the lfs advice, because I’m afraid they try to sell a lot of meds. Do you think it’s better bring the photos to them and try to get advice from them?

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