Corydoras bloodshot mouth

[AlexT]

This week I have upgraded from a 110 litre to a 180 litre tank and obviously moved the fish. Injury?

No other fish seem to have this. I don't think there is any water quality problems. I've not seem ammonia or nitrite in this, my main set up and test a few times a week as still fairly newly established. Nitrate has never been more than 20 and in recent times, 10 at most.

Tank: 180L
Water: 70% RO and 30% Tap
Substrate: Sand
Driftwood: i cant see anything sharp
Occupants: Corydoras (21), white fin bentosi tetra (21), Small Ancistrus (4)
Water: Temp 76 pH 7.4, KH 4, GH 5, Ammonia Nil, Nitrite Nil, Nitrate 10 -
Water changes: 70% 13 days ago, 40% 6 days ago and 2 days ago they moved over from a 110L to a 180L with 50% fresh water added.

Most recent additions: 8 corydoras and 2 ancistrus who were QT for 2 weeks and no signs of poor health or worrying behaviour.

 

[Byron]

Might be red blotch, but others will have to confirm, I have no experience with fish ailments and won't guess.

 

[Colin_T]

Physical injury.
Keep the tank clean and it should heal up by itself.
Monitor for white fluffy stuff (fungus) or the red area spreading (bacterial).
you can add a bit of salt if it looks like it's infected.

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SALT
You can add rock salt (often sold as aquarium salt), swimming pool salt, or any non iodised salt (sodium chloride) to the aquarium at the dose rate of 1 heaped tablespoon per 20 litres (5 gallons) of water. If there is no improvement after 48 hours you can double that dose rate so there is 2 heaped tablespoons of salt per 20 litres.

Keep the salt level like this for 1-2 weeks.

The salt will not affect the beneficial filter bacteria, 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.

When you first add salt, add the salt to a small bucket of tank water and dissolve the salt. Then slowly pour the salt water into the tank near the filter outlet. Add the salt over a couple of minutes.