Very Sick Cory - Red Blotch Disease?

[FashionFish]

If you do regular (weekly) water changes, the aquarium water and tap water should have similar water chemistry values (GH, KH, pH). So doing a large water change (75-80%) won't harm the fish as long as the new water has a similar temperature to the aquarium water, and the new water is free of chlorine/ chloramine before it's added to the tank.

The substrate might not be releasing anything now but there might be gunk trapped in it that could be contributing to skin irritation. Gravel cleaning the substrate at least once a month would help remove a lot of the harmful disease organisms that live in rotting fish waste.

Ok, got it! Thank you again!

 

[AdoraBelle Dearheart]

Ok, got it! Thank you again!

How are the cories now? Have been sending good vibes your way, it's clear you care about them a lot, and I wish we had a simple answer for you! Sadly, it's rarely simple when it comes to fish health! How are they behaving and looking now?

 

[FashionFish]

How are the cories now? Have been sending good vibes your way, it's clear you care about them a lot, and I wish we had a simple answer for you! Sadly, it's rarely simple when it comes to fish health! How are they behaving and looking now?

Thank you for the good vibes Adorabelle! We do care about our aquatic pets a lot. Definitely are attached after years of enjoying them.

The fish are swimming happily, have not seen any flashing in a few days. There is still the redness but we will continue the water changes and look for more progress. Will for sure keep you posted.

 

[shaurdav]

Maybe these fish develop these spots with age.