Corydoras flashing, possible bully issue

[Colin_T]

Black substrate and bubbles that smell like rotten eggs (hydrogen sulphide) is normally caused by rotting matter in the substrate. If large amounts of the gas are released at the same time, it can poison the fish and they either gasp at the surface or just die straight away.

If you used a gravel cleaner when it happened, most of the bad gas would have been drawn out with the water and very little would have remained in the tank. This is one reason why a gravel cleaner is much safer and better than stirring up the gravel and sucking gunk out after.

It is possible that anaerobic bacteria in the substrate is contributing to the Corydoras issue. The Cories are in direct contact with the dirty gravel/ sand and will be more likely to suffer than fish that are not in contact with the substrate.

Removing the dirty sand/ gravel will not affect the filter bacteria, which should be living in the filter.

If you gravel clean the sand and get rid of the stinky bubbles, the sand should clear up over time (and with more gravel cleans), as the aerobic bacteria get rid of the anaerobic bacteria. The anaerobic bacteria cause the substrate to go black.

 

[Jwgoff7772]

Does this look like velvet?

I was looking at my fish last night and noticed alot of gold coloration on all my cories that I've never noticed before. It could have always and been there and maybe now since they are not feeling well maybe I'm noticing things I didnt noticed before.

In the video you'll see very small specs on top his dorsal as well but you can especially see it mostly around his gills going all the way to his tail. Youllnalso see hun flash again in the video. I've read because of cories "armor" it's harder ti detect parasites that live on this fishes skin and not be as obvious when a cories has a external parasite but not sure if that's true. Please tell me what you think

The video maybe a little shaky for which I apologize, its not easy trying to film a moving fish with a phone camera.